How do I determine the size of an object in Python

Question

I want to know how to get size of objects like a string  integer  etc  in Python   Related question  How many bytes per element are there in a Python list  tuple    I am using an XML file which contains size fields that specify the size of value  I must parse this XML and do my coding  When I want to change the value of a particular field  I will check the size field of that value  Here I want to compare whether the new value that I m gong to enter is of the same size as in XML  I need to check the size of new value  In case of a string I can say its the length  But in case of int  float  etc  I am confused

User · Answer

Here is a quick script I  wrote based on the previous answers to list sizes of all variables  for i in dir        print  i  sys getsizeof eval i

User · Answer

You can serialize the object to derive a measure that is closely related to the size of the object  import pickle     let o be the object whose size you want to measure size estimate   len pickle dumps o    If you want to measure objects that cannot be pickled  e g  because of lambda expressions  dill or cloudpickle can be a solution

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Use sys getsizeof   if you DON T want to include sizes of linked  nested  objects    However  if you want to count sub-objects nested in lists  dicts  sets  tuples - and usually THIS is what you re looking for - use the recursive deep sizeof   function as shown below   import sys def sizeof obj       size   sys getsizeof obj      if isinstance obj  dict   return size   sum map sizeof  obj keys       sum map sizeof  obj values         if isinstance obj   list  tuple  set  frozenset    return size   sum map sizeof  obj       return size   You can also find this function in the nifty toolbox  together with many other useful one-liners   https   github com mwojnars nifty blob master util py

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You can make use of getSizeof   as mentioned below to determine the size of an object  import sys str1    one  int element 5 print  Memory size of    str1        str sys getsizeof str1      bytes   print  Memory size of     str int element         str sys getsizeof int element      bytes

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You can serialize the object to derive a measure that is closely related to the size of the object  import pickle     let o be the object whose size you want to measure size estimate   len pickle dumps o    If you want to measure objects that cannot be pickled  e g  because of lambda expressions  dill or cloudpickle can be a solution

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The Pympler package s asizeof module can do this   Use as follows   from pympler import asizeof asizeof asizeof my object    Unlike sys getsizeof  it works for your self-created objects  It even works with numpy    gt  gt  gt  asizeof asizeof tuple  bcd    200  gt  gt  gt  asizeof asizeof   foo    bar    baz    bar    400  gt  gt  gt  asizeof asizeof     280  gt  gt  gt  asizeof asizeof   foo   bar    360  gt  gt  gt  asizeof asizeof  foo   40  gt  gt  gt  asizeof asizeof Bar    352  gt  gt  gt  asizeof asizeof Bar     dict    280  gt  gt  gt  A   rand 10   gt  gt  gt  B   rand 10000   gt  gt  gt  asizeof asizeof A  176  gt  gt  gt  asizeof asizeof B  80096   As mentioned      The  byte code size of objects like classes  functions  methods  modules  etc  can be included by setting option code True    And if you need other view on live data  Pympler s      module muppy is used for on-line monitoring of a Python application   and module Class Tracker provides off-line analysis of the lifetime of   selected Python objects

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Just use the sys getsizeof function defined in the sys module   sys getsizeof object   default    Return the size of an object in bytes  The object can be any type of object  All built-in objects will return correct results  but this does not have to hold true for third-party extensions as it is implementation specific  Only the memory consumption directly attributed to the object is accounted for  not the memory consumption of objects it refers to  The default argument allows to define a value which will be returned if the object type does not provide means to retrieve the size and would cause a TypeError  getsizeof calls the object   s   sizeof   method and adds an additional garbage collector overhead if the object is managed by the garbage collector  See recursive sizeof recipe for an example of using getsizeof   recursively to find the size of containers and all their contents   Usage example  in python 3 0   gt  gt  gt  import sys  gt  gt  gt  x   2  gt  gt  gt  sys getsizeof x  24  gt  gt  gt  sys getsizeof sys getsizeof  32  gt  gt  gt  sys getsizeof  this   38  gt  gt  gt  sys getsizeof  this also   48  If you are in python  lt  2 6 and don t have sys getsizeof you can use this extensive module instead  Never used it though

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Here is a quick script I  wrote based on the previous answers to list sizes of all variables  for i in dir        print  i  sys getsizeof eval i

User · Answer

If you don t need the exact size of the object but roughly to know how big it is  one quick  and dirty  way is to let the program run  sleep for an extended period of time  and check the memory usage  ex  Mac s activity monitor  by this particular python process  This would be effective when you are trying to find the size of one single large object in a python process  For example  I recently wanted to check the memory usage of a new data structure and compare it with that of Python s set data structure  First I wrote the elements  words from a large public domain book  to a set  then checked the size of the process  and then did the same thing with the other data structure  I found out the Python process with a set is taking twice as much memory as the new data structure  Again  you wouldn t be able to exactly say the memory used by the process is equal to the size of the object  As the size of the object gets large  this becomes close as the memory consumed by the rest of the process becomes negligible compared to the size of the object you are trying to monitor

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I use this trick    May won t be accurate on small objects  but I think it s much more accurate for a complex object  like pygame surface  rather than sys getsizeof    import pygame as pg import os import psutil import time   process   psutil Process os getpid    pg init       vocab     hello    me    you    she    he    they    we             should    why     necessarily    do    that    font   pg font SysFont  monospace   100  True   dct       newMem   process memory info   rss    don t mind this line Str   f store     f Nothing  tsurface use about   expandtabs 15            f 0 t bytes  expandtabs 9     don t mind this assignment too  usedMem   process memory info   rss  for word in vocab      dct word    font render word  True  pg Color   000000         time sleep 0 1     wait a moment        get total used memory of this script      newMem   process memory info   rss     Str   f store     f  word  tsurface use about   expandtabs 15                f  newMem - usedMem  t bytes  expandtabs 9       print Str      usedMem   newMem   On my windows 10  python 3 7 3  the output is   store hello          surface use about 225280    bytes store me             surface use about 61440     bytes store you            surface use about 94208     bytes store she            surface use about 81920     bytes store he             surface use about 53248     bytes store they           surface use about 114688    bytes store we             surface use about 57344     bytes store should         surface use about 172032    bytes store why            surface use about 110592    bytes store necessarily    surface use about 311296    bytes store do             surface use about 57344     bytes store that           surface use about 110592    bytes

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How do I determine the size of an object in Python   The answer   quot Just use sys getsizeof quot   is not a complete answer  That answer does work for builtin objects directly  but it does not account for what those objects may contain  specifically  what types  such as custom objects  tuples  lists  dicts  and sets contain  They can contain instances each other  as well as numbers  strings and other objects  A More Complete Answer Using 64-bit Python 3 6 from the Anaconda distribution  with sys getsizeof  I have determined the minimum size of the following objects  and note that sets and dicts preallocate space so empty ones don t grow again until after a set amount  which may vary by implementation of the language   Python 3  Empty Bytes  type        scaling notes 28     int          4 bytes about every 30 powers of 2 37     bytes        1 byte per additional byte 49     str          1-4 per additional character  depending on max width  48     tuple        8 per additional item 64     list         8 for each additional 224    set         5th increases to 736  21nd  2272  85th  8416  341  32992 240    dict        6th increases to 368  22nd  1184  43rd  2280  86th  4704  171st  9320 136    func def    does not include default args and other attrs 1056   class def   no slots  56     class inst  has a   dict   attr  same scaling as dict above 888    class def   with slots 16       slots     seems to store in mutable tuple-like structure                    first slot grows to 48  and so on   How do you interpret this  Well say you have a set with 10 items in it  If each item is 100 bytes each  how big is the whole data structure  The set is 736 itself because it has sized up one time to 736 bytes  Then you add the size of the items  so that s 1736 bytes in total Some caveats for function and class definitions  Note each class definition has a proxy   dict    48 bytes  structure for class attrs  Each slot has a descriptor  like a property  in the class definition  Slotted instances start out with 48 bytes on their first element  and increase by 8 each additional  Only empty slotted objects have 16 bytes  and an instance with no data makes very little sense  Also  each function definition has code objects  maybe docstrings  and other possible attributes  even a   dict    Also note that we use sys getsizeof   because we care about the marginal space usage  which includes the garbage collection overhead for the object  from the docs   getsizeof   calls the object   s   sizeof   method and adds an additional garbage collector overhead if the object is managed by the garbage collector   Also note that resizing lists  e g  repetitively appending to them  causes them to preallocate space  similarly to sets and dicts  From the listobj c source code         This over-allocates proportional to the list size  making room        for additional growth   The over-allocation is mild  but is        enough to give linear-time amortized behavior over a long        sequence of appends   in the presence of a poorly-performing        system realloc           The growth pattern is   0  4  8  16  25  35  46  58  72  88             Note  new allocated won t overflow because the largest possible value              is PY SSIZE T MAX    9   8    6 which always fits in a size t              new allocated    size t newsize    newsize  gt  gt  3     newsize  lt  9   3   6    Historical data Python 2 7 analysis  confirmed with guppy hpy and sys getsizeof  Bytes  type        empty   scaling notes 24     int         NA 28     long        NA 37     str           1 byte per additional character 52     unicode       4 bytes per additional character 56     tuple         8 bytes per additional item 72     list          32 for first  8 for each additional 232    set         sixth item increases to 744  22nd  2280  86th  8424 280    dict        sixth item increases to 1048  22nd  3352  86th  12568   120    func def    does not include default args and other attrs 64     class inst  has a   dict   attr  same scaling as dict above 16       slots     class with slots has no dict  seems to store in                      mutable tuple-like structure  904    class def   has a proxy   dict   structure for class attrs 104    old class   makes sense  less stuff  has real dict though   Note that dictionaries  but not sets  got a more compact representation in Python 3 6 I think 8 bytes per additional item to reference makes a lot of sense on a 64 bit machine  Those 8 bytes point to the place in memory the contained item is at  The 4 bytes are fixed width for unicode in Python 2  if I recall correctly  but in Python 3  str becomes a unicode of width equal to the max width of the characters  And for more on slots  see this answer  A More Complete Function We want a function that searches the elements in lists  tuples  sets  dicts  obj   dict   s  and obj   slots    as well as other things we may not have yet thought of  We want to rely on gc get referents to do this search because it works at the C level  making it very fast   The downside is that get referents can return redundant members  so we need to ensure we don t double count  Classes  modules  and functions are singletons - they exist one time in memory  We re not so interested in their size  as there s not much we can do about them - they re a part of the program  So we ll avoid counting them if they happen to be referenced  We re going to use a blacklist of types so we don t include the entire program in our size count  import sys from types import ModuleType  FunctionType from gc import get referents    Custom objects know their class    Function objects seem to know way too much  including modules    Exclude modules as well  BLACKLIST   type  ModuleType  FunctionType   def getsize obj        quot  quot  quot sum size of object  amp  members  quot  quot  quot      if isinstance obj  BLACKLIST           raise TypeError  getsize   does not take argument of type     str type obj        seen ids   set       size   0     objects    obj      while objects          need referents              for obj in objects              if not isinstance obj  BLACKLIST  and id obj  not in seen ids                  seen ids add id obj                   size    sys getsizeof obj                  need referents append obj          objects   get referents  need referents      return size  To contrast this with the following whitelisted function  most objects know how to traverse themselves for the purposes of garbage collection  which is approximately what we re looking for when we want to know how expensive in memory certain objects are  This functionality is used by gc get referents   However  this measure is going to be much more expansive in scope than we intended if we are not careful  For example  functions know quite a lot about the modules they are created in  Another point of contrast is that strings that are keys in dictionaries are usually interned so they are not duplicated  Checking for id key  will also allow us to avoid counting duplicates  which we do in the next section  The blacklist solution skips counting keys that are strings altogether  Whitelisted Types  Recursive visitor  old implementation  To cover most of these types myself  instead of relying on the gc module  I wrote this recursive function to try to estimate the size of most Python objects  including most builtins  types in the collections module  and custom types  slotted and otherwise   This sort of function gives much more fine-grained control over the types we re going to count for memory usage  but has the danger of leaving types out  import sys from numbers import Number from collections import Set  Mapping  deque  try    Python 2     zero depth bases    basestring  Number  xrange  bytearray      iteritems    iteritems  except NameError    Python 3     zero depth bases    str  bytes  Number  range  bytearray      iteritems    items   def getsize obj 0        quot  quot  quot Recursively iterate to sum size of object  amp  members  quot  quot  quot       seen ids   set       def inner obj           obj id   id obj          if obj id in  seen ids              return 0          seen ids add obj id          size   sys getsizeof obj          if isinstance obj  zero depth bases               pass   bypass remaining control flow and return         elif isinstance obj   tuple  list  Set  deque                size    sum inner i  for i in obj          elif isinstance obj  Mapping  or hasattr obj  iteritems               size    sum inner k    inner v  for k  v in getattr obj  iteritems               Check for custom object instances - may subclass above too         if hasattr obj     dict                  size    inner vars obj           if hasattr obj     slots        can have   slots   with   dict               size    sum inner getattr obj  s   for s in obj   slots   if hasattr obj  s           return size     return inner obj 0   And I tested it rather casually  I should unittest it    gt  gt  gt  getsize   a   tuple  bcd    Foo     344  gt  gt  gt  getsize Foo    16  gt  gt  gt  getsize tuple  bcd    194  gt  gt  gt  getsize   a   tuple  bcd    Foo      foo    bar    baz    bar     752  gt  gt  gt  getsize   foo    bar    baz    bar    400  gt  gt  gt  getsize     280  gt  gt  gt  getsize   foo   bar    360  gt  gt  gt  getsize  foo   40  gt  gt  gt  class Bar            def baz                pass  gt  gt  gt  getsize Bar    352  gt  gt  gt  getsize Bar     dict    280  gt  gt  gt  sys getsizeof Bar    72  gt  gt  gt  getsize Bar   dict    872  gt  gt  gt  sys getsizeof Bar   dict    280  This implementation breaks down on class definitions and function definitions because we don t go after all of their attributes  but since they should only exist once in memory for the process  their size really doesn t matter too much

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This can be more complicated than it looks depending on how you want to count things   For instance  if you have a list of ints  do you want the size of the list containing the references to the ints   ie  list only  not what is contained in it   or do you want to include the actual data pointed to  in which case you need to deal with duplicate references  and how to prevent double-counting when two objects contain references to the same object    You may want to take a look at one of the python memory profilers  such as pysizer to see if they meet your needs

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You can make use of getSizeof   as mentioned below to determine the size of an object  import sys str1    one  int element 5 print  Memory size of    str1        str sys getsizeof str1      bytes   print  Memory size of     str int element         str sys getsizeof int element      bytes

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Python 3 8  Q1 2019  will change some of the results of sys getsizeof  as announced here by Raymond Hettinger      Python containers are 8 bytes smaller on 64-bit builds    tuple     48 - gt  40        list      64 - gt 56 set      224 - gt  216 dict     240 - gt  232   This comes after issue 33597 and Inada Naoki  methane  s work around Compact PyGC Head  and PR 7043     This idea reduces PyGC Head size to two words       Currently  PyGC Head takes three words  gc prev  gc next  and gc refcnt          gc refcnt is used when collecting  for trial deletion    gc prev is used for tracking and untracking          So if we can avoid tracking untracking while trial deletion  gc prev and gc refcnt can share same memory space    See commit d5c875b      Removed one Py ssize t member from PyGC Head    All GC tracked objects  e g  tuple  list  dict  size is reduced 4 or 8 bytes

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Use sys getsizeof   if you DON T want to include sizes of linked  nested  objects    However  if you want to count sub-objects nested in lists  dicts  sets  tuples - and usually THIS is what you re looking for - use the recursive deep sizeof   function as shown below   import sys def sizeof obj       size   sys getsizeof obj      if isinstance obj  dict   return size   sum map sizeof  obj keys       sum map sizeof  obj values         if isinstance obj   list  tuple  set  frozenset    return size   sum map sizeof  obj       return size   You can also find this function in the nifty toolbox  together with many other useful one-liners   https   github com mwojnars nifty blob master util py

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Having run into this problem many times myself  I wrote up a small function  inspired by  aaron-hall s answer   amp  tests that does what I would have expected sys getsizeof to do   https   github com bosswissam pysize  If you re interested in the backstory  here it is  EDIT  Attaching the code below for easy reference  To see the most up-to-date code  please check the github link       import sys      def get size obj  seen None              Recursively finds size of objects            size   sys getsizeof obj          if seen is None              seen   set           obj id   id obj          if obj id in seen              return 0           Important mark as seen  before  entering recursion to gracefully handle           self-referential objects         seen add obj id          if isinstance obj  dict               size    sum  get size v  seen  for v in obj values                 size    sum  get size k  seen  for k in obj keys             elif hasattr obj     dict                  size    get size obj   dict    seen          elif hasattr obj     iter     and not isinstance obj   str  bytes  bytearray                size    sum  get size i  seen  for i in obj           return size

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How do I determine the size of an object in Python   The answer   quot Just use sys getsizeof quot   is not a complete answer  That answer does work for builtin objects directly  but it does not account for what those objects may contain  specifically  what types  such as custom objects  tuples  lists  dicts  and sets contain  They can contain instances each other  as well as numbers  strings and other objects  A More Complete Answer Using 64-bit Python 3 6 from the Anaconda distribution  with sys getsizeof  I have determined the minimum size of the following objects  and note that sets and dicts preallocate space so empty ones don t grow again until after a set amount  which may vary by implementation of the language   Python 3  Empty Bytes  type        scaling notes 28     int          4 bytes about every 30 powers of 2 37     bytes        1 byte per additional byte 49     str          1-4 per additional character  depending on max width  48     tuple        8 per additional item 64     list         8 for each additional 224    set         5th increases to 736  21nd  2272  85th  8416  341  32992 240    dict        6th increases to 368  22nd  1184  43rd  2280  86th  4704  171st  9320 136    func def    does not include default args and other attrs 1056   class def   no slots  56     class inst  has a   dict   attr  same scaling as dict above 888    class def   with slots 16       slots     seems to store in mutable tuple-like structure                    first slot grows to 48  and so on   How do you interpret this  Well say you have a set with 10 items in it  If each item is 100 bytes each  how big is the whole data structure  The set is 736 itself because it has sized up one time to 736 bytes  Then you add the size of the items  so that s 1736 bytes in total Some caveats for function and class definitions  Note each class definition has a proxy   dict    48 bytes  structure for class attrs  Each slot has a descriptor  like a property  in the class definition  Slotted instances start out with 48 bytes on their first element  and increase by 8 each additional  Only empty slotted objects have 16 bytes  and an instance with no data makes very little sense  Also  each function definition has code objects  maybe docstrings  and other possible attributes  even a   dict    Also note that we use sys getsizeof   because we care about the marginal space usage  which includes the garbage collection overhead for the object  from the docs   getsizeof   calls the object   s   sizeof   method and adds an additional garbage collector overhead if the object is managed by the garbage collector   Also note that resizing lists  e g  repetitively appending to them  causes them to preallocate space  similarly to sets and dicts  From the listobj c source code         This over-allocates proportional to the list size  making room        for additional growth   The over-allocation is mild  but is        enough to give linear-time amortized behavior over a long        sequence of appends   in the presence of a poorly-performing        system realloc           The growth pattern is   0  4  8  16  25  35  46  58  72  88             Note  new allocated won t overflow because the largest possible value              is PY SSIZE T MAX    9   8    6 which always fits in a size t              new allocated    size t newsize    newsize  gt  gt  3     newsize  lt  9   3   6    Historical data Python 2 7 analysis  confirmed with guppy hpy and sys getsizeof  Bytes  type        empty   scaling notes 24     int         NA 28     long        NA 37     str           1 byte per additional character 52     unicode       4 bytes per additional character 56     tuple         8 bytes per additional item 72     list          32 for first  8 for each additional 232    set         sixth item increases to 744  22nd  2280  86th  8424 280    dict        sixth item increases to 1048  22nd  3352  86th  12568   120    func def    does not include default args and other attrs 64     class inst  has a   dict   attr  same scaling as dict above 16       slots     class with slots has no dict  seems to store in                      mutable tuple-like structure  904    class def   has a proxy   dict   structure for class attrs 104    old class   makes sense  less stuff  has real dict though   Note that dictionaries  but not sets  got a more compact representation in Python 3 6 I think 8 bytes per additional item to reference makes a lot of sense on a 64 bit machine  Those 8 bytes point to the place in memory the contained item is at  The 4 bytes are fixed width for unicode in Python 2  if I recall correctly  but in Python 3  str becomes a unicode of width equal to the max width of the characters  And for more on slots  see this answer  A More Complete Function We want a function that searches the elements in lists  tuples  sets  dicts  obj   dict   s  and obj   slots    as well as other things we may not have yet thought of  We want to rely on gc get referents to do this search because it works at the C level  making it very fast   The downside is that get referents can return redundant members  so we need to ensure we don t double count  Classes  modules  and functions are singletons - they exist one time in memory  We re not so interested in their size  as there s not much we can do about them - they re a part of the program  So we ll avoid counting them if they happen to be referenced  We re going to use a blacklist of types so we don t include the entire program in our size count  import sys from types import ModuleType  FunctionType from gc import get referents    Custom objects know their class    Function objects seem to know way too much  including modules    Exclude modules as well  BLACKLIST   type  ModuleType  FunctionType   def getsize obj        quot  quot  quot sum size of object  amp  members  quot  quot  quot      if isinstance obj  BLACKLIST           raise TypeError  getsize   does not take argument of type     str type obj        seen ids   set       size   0     objects    obj      while objects          need referents              for obj in objects              if not isinstance obj  BLACKLIST  and id obj  not in seen ids                  seen ids add id obj                   size    sys getsizeof obj                  need referents append obj          objects   get referents  need referents      return size  To contrast this with the following whitelisted function  most objects know how to traverse themselves for the purposes of garbage collection  which is approximately what we re looking for when we want to know how expensive in memory certain objects are  This functionality is used by gc get referents   However  this measure is going to be much more expansive in scope than we intended if we are not careful  For example  functions know quite a lot about the modules they are created in  Another point of contrast is that strings that are keys in dictionaries are usually interned so they are not duplicated  Checking for id key  will also allow us to avoid counting duplicates  which we do in the next section  The blacklist solution skips counting keys that are strings altogether  Whitelisted Types  Recursive visitor  old implementation  To cover most of these types myself  instead of relying on the gc module  I wrote this recursive function to try to estimate the size of most Python objects  including most builtins  types in the collections module  and custom types  slotted and otherwise   This sort of function gives much more fine-grained control over the types we re going to count for memory usage  but has the danger of leaving types out  import sys from numbers import Number from collections import Set  Mapping  deque  try    Python 2     zero depth bases    basestring  Number  xrange  bytearray      iteritems    iteritems  except NameError    Python 3     zero depth bases    str  bytes  Number  range  bytearray      iteritems    items   def getsize obj 0        quot  quot  quot Recursively iterate to sum size of object  amp  members  quot  quot  quot       seen ids   set       def inner obj           obj id   id obj          if obj id in  seen ids              return 0          seen ids add obj id          size   sys getsizeof obj          if isinstance obj  zero depth bases               pass   bypass remaining control flow and return         elif isinstance obj   tuple  list  Set  deque                size    sum inner i  for i in obj          elif isinstance obj  Mapping  or hasattr obj  iteritems               size    sum inner k    inner v  for k  v in getattr obj  iteritems               Check for custom object instances - may subclass above too         if hasattr obj     dict                  size    inner vars obj           if hasattr obj     slots        can have   slots   with   dict               size    sum inner getattr obj  s   for s in obj   slots   if hasattr obj  s           return size     return inner obj 0   And I tested it rather casually  I should unittest it    gt  gt  gt  getsize   a   tuple  bcd    Foo     344  gt  gt  gt  getsize Foo    16  gt  gt  gt  getsize tuple  bcd    194  gt  gt  gt  getsize   a   tuple  bcd    Foo      foo    bar    baz    bar     752  gt  gt  gt  getsize   foo    bar    baz    bar    400  gt  gt  gt  getsize     280  gt  gt  gt  getsize   foo   bar    360  gt  gt  gt  getsize  foo   40  gt  gt  gt  class Bar            def baz                pass  gt  gt  gt  getsize Bar    352  gt  gt  gt  getsize Bar     dict    280  gt  gt  gt  sys getsizeof Bar    72  gt  gt  gt  getsize Bar   dict    872  gt  gt  gt  sys getsizeof Bar   dict    280  This implementation breaks down on class definitions and function definitions because we don t go after all of their attributes  but since they should only exist once in memory for the process  their size really doesn t matter too much

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Just use the sys getsizeof function defined in the sys module   sys getsizeof object   default    Return the size of an object in bytes  The object can be any type of object  All built-in objects will return correct results  but this does not have to hold true for third-party extensions as it is implementation specific  Only the memory consumption directly attributed to the object is accounted for  not the memory consumption of objects it refers to  The default argument allows to define a value which will be returned if the object type does not provide means to retrieve the size and would cause a TypeError  getsizeof calls the object   s   sizeof   method and adds an additional garbage collector overhead if the object is managed by the garbage collector  See recursive sizeof recipe for an example of using getsizeof   recursively to find the size of containers and all their contents   Usage example  in python 3 0   gt  gt  gt  import sys  gt  gt  gt  x   2  gt  gt  gt  sys getsizeof x  24  gt  gt  gt  sys getsizeof sys getsizeof  32  gt  gt  gt  sys getsizeof  this   38  gt  gt  gt  sys getsizeof  this also   48  If you are in python  lt  2 6 and don t have sys getsizeof you can use this extensive module instead  Never used it though

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If you don t need the exact size of the object but roughly to know how big it is  one quick  and dirty  way is to let the program run  sleep for an extended period of time  and check the memory usage  ex  Mac s activity monitor  by this particular python process  This would be effective when you are trying to find the size of one single large object in a python process  For example  I recently wanted to check the memory usage of a new data structure and compare it with that of Python s set data structure  First I wrote the elements  words from a large public domain book  to a set  then checked the size of the process  and then did the same thing with the other data structure  I found out the Python process with a set is taking twice as much memory as the new data structure  Again  you wouldn t be able to exactly say the memory used by the process is equal to the size of the object  As the size of the object gets large  this becomes close as the memory consumed by the rest of the process becomes negligible compared to the size of the object you are trying to monitor

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I use this trick    May won t be accurate on small objects  but I think it s much more accurate for a complex object  like pygame surface  rather than sys getsizeof    import pygame as pg import os import psutil import time   process   psutil Process os getpid    pg init       vocab     hello    me    you    she    he    they    we             should    why     necessarily    do    that    font   pg font SysFont  monospace   100  True   dct       newMem   process memory info   rss    don t mind this line Str   f store     f Nothing  tsurface use about   expandtabs 15            f 0 t bytes  expandtabs 9     don t mind this assignment too  usedMem   process memory info   rss  for word in vocab      dct word    font render word  True  pg Color   000000         time sleep 0 1     wait a moment        get total used memory of this script      newMem   process memory info   rss     Str   f store     f  word  tsurface use about   expandtabs 15                f  newMem - usedMem  t bytes  expandtabs 9       print Str      usedMem   newMem   On my windows 10  python 3 7 3  the output is   store hello          surface use about 225280    bytes store me             surface use about 61440     bytes store you            surface use about 94208     bytes store she            surface use about 81920     bytes store he             surface use about 53248     bytes store they           surface use about 114688    bytes store we             surface use about 57344     bytes store should         surface use about 172032    bytes store why            surface use about 110592    bytes store necessarily    surface use about 311296    bytes store do             surface use about 57344     bytes store that           surface use about 110592    bytes

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Just use the sys getsizeof function defined in the sys module   sys getsizeof object   default    Return the size of an object in bytes  The object can be any type of object  All built-in objects will return correct results  but this does not have to hold true for third-party extensions as it is implementation specific  Only the memory consumption directly attributed to the object is accounted for  not the memory consumption of objects it refers to  The default argument allows to define a value which will be returned if the object type does not provide means to retrieve the size and would cause a TypeError  getsizeof calls the object   s   sizeof   method and adds an additional garbage collector overhead if the object is managed by the garbage collector  See recursive sizeof recipe for an example of using getsizeof   recursively to find the size of containers and all their contents   Usage example  in python 3 0   gt  gt  gt  import sys  gt  gt  gt  x   2  gt  gt  gt  sys getsizeof x  24  gt  gt  gt  sys getsizeof sys getsizeof  32  gt  gt  gt  sys getsizeof  this   38  gt  gt  gt  sys getsizeof  this also   48  If you are in python  lt  2 6 and don t have sys getsizeof you can use this extensive module instead  Never used it though

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Just use the sys getsizeof function defined in the sys module   sys getsizeof object   default    Return the size of an object in bytes  The object can be any type of object  All built-in objects will return correct results  but this does not have to hold true for third-party extensions as it is implementation specific  Only the memory consumption directly attributed to the object is accounted for  not the memory consumption of objects it refers to  The default argument allows to define a value which will be returned if the object type does not provide means to retrieve the size and would cause a TypeError  getsizeof calls the object   s   sizeof   method and adds an additional garbage collector overhead if the object is managed by the garbage collector  See recursive sizeof recipe for an example of using getsizeof   recursively to find the size of containers and all their contents   Usage example  in python 3 0   gt  gt  gt  import sys  gt  gt  gt  x   2  gt  gt  gt  sys getsizeof x  24  gt  gt  gt  sys getsizeof sys getsizeof  32  gt  gt  gt  sys getsizeof  this   38  gt  gt  gt  sys getsizeof  this also   48  If you are in python  lt  2 6 and don t have sys getsizeof you can use this extensive module instead  Never used it though

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For numpy arrays  getsizeof doesn t work - for me it always returns 40 for some reason   from pylab import   from sys import getsizeof A   rand 10  B   rand 10000    Then  in ipython    In  64   getsizeof A  Out 64   40  In  65   getsizeof B  Out 65   40   Happily  though   In  66   A nbytes Out 66   80  In  67   B nbytes Out 67   80000

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The Pympler package s asizeof module can do this   Use as follows   from pympler import asizeof asizeof asizeof my object    Unlike sys getsizeof  it works for your self-created objects  It even works with numpy    gt  gt  gt  asizeof asizeof tuple  bcd    200  gt  gt  gt  asizeof asizeof   foo    bar    baz    bar    400  gt  gt  gt  asizeof asizeof     280  gt  gt  gt  asizeof asizeof   foo   bar    360  gt  gt  gt  asizeof asizeof  foo   40  gt  gt  gt  asizeof asizeof Bar    352  gt  gt  gt  asizeof asizeof Bar     dict    280  gt  gt  gt  A   rand 10   gt  gt  gt  B   rand 10000   gt  gt  gt  asizeof asizeof A  176  gt  gt  gt  asizeof asizeof B  80096   As mentioned      The  byte code size of objects like classes  functions  methods  modules  etc  can be included by setting option code True    And if you need other view on live data  Pympler s      module muppy is used for on-line monitoring of a Python application   and module Class Tracker provides off-line analysis of the lifetime of   selected Python objects

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This can be more complicated than it looks depending on how you want to count things   For instance  if you have a list of ints  do you want the size of the list containing the references to the ints   ie  list only  not what is contained in it   or do you want to include the actual data pointed to  in which case you need to deal with duplicate references  and how to prevent double-counting when two objects contain references to the same object    You may want to take a look at one of the python memory profilers  such as pysizer to see if they meet your needs

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Python 3 8  Q1 2019  will change some of the results of sys getsizeof  as announced here by Raymond Hettinger      Python containers are 8 bytes smaller on 64-bit builds    tuple     48 - gt  40        list      64 - gt 56 set      224 - gt  216 dict     240 - gt  232   This comes after issue 33597 and Inada Naoki  methane  s work around Compact PyGC Head  and PR 7043     This idea reduces PyGC Head size to two words       Currently  PyGC Head takes three words  gc prev  gc next  and gc refcnt          gc refcnt is used when collecting  for trial deletion    gc prev is used for tracking and untracking          So if we can avoid tracking untracking while trial deletion  gc prev and gc refcnt can share same memory space    See commit d5c875b      Removed one Py ssize t member from PyGC Head    All GC tracked objects  e g  tuple  list  dict  size is reduced 4 or 8 bytes

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For numpy arrays  getsizeof doesn t work - for me it always returns 40 for some reason   from pylab import   from sys import getsizeof A   rand 10  B   rand 10000    Then  in ipython    In  64   getsizeof A  Out 64   40  In  65   getsizeof B  Out 65   40   Happily  though   In  66   A nbytes Out 66   80  In  67   B nbytes Out 67   80000

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Having run into this problem many times myself  I wrote up a small function  inspired by  aaron-hall s answer   amp  tests that does what I would have expected sys getsizeof to do   https   github com bosswissam pysize  If you re interested in the backstory  here it is  EDIT  Attaching the code below for easy reference  To see the most up-to-date code  please check the github link       import sys      def get size obj  seen None              Recursively finds size of objects            size   sys getsizeof obj          if seen is None              seen   set           obj id   id obj          if obj id in seen              return 0           Important mark as seen  before  entering recursion to gracefully handle           self-referential objects         seen add obj id          if isinstance obj  dict               size    sum  get size v  seen  for v in obj values                 size    sum  get size k  seen  for k in obj keys             elif hasattr obj     dict                  size    get size obj   dict    seen          elif hasattr obj     iter     and not isinstance obj   str  bytes  bytearray                size    sum  get size i  seen  for i in obj           return size

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This can be more complicated than it looks depending on how you want to count things   For instance  if you have a list of ints  do you want the size of the list containing the references to the ints   ie  list only  not what is contained in it   or do you want to include the actual data pointed to  in which case you need to deal with duplicate references  and how to prevent double-counting when two objects contain references to the same object    You may want to take a look at one of the python memory profilers  such as pysizer to see if they meet your needs

User · Answer

This can be more complicated than it looks depending on how you want to count things   For instance  if you have a list of ints  do you want the size of the list containing the references to the ints   ie  list only  not what is contained in it   or do you want to include the actual data pointed to  in which case you need to deal with duplicate references  and how to prevent double-counting when two objects contain references to the same object    You may want to take a look at one of the python memory profilers  such as pysizer to see if they meet your needs

[python] How do I determine the size of an object in Python?

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