How do I look inside a Python object

Question

I m starting to code in various projects using Python  including Django web development and Panda3D game development     To help me understand what s going on  I would like to basically  look  inside the Python objects to see how they tick - like their methods and properties    So say I have a Python object  what would I need to print out its contents  Is that even possible

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Many good tipps already  but the shortest and easiest  not necessarily the best  has yet to be mentioned    object

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First  read the source   Second  use the dir   function

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Visit http   diveintopython net        author      Mark Pilgrim  mark diveintopython org     def info object  spacing 10  collapse 1          Print methods and doc strings       Takes module  class  list  dictionary  or string         methodList    e for e in dir object  if callable getattr object  e        processFunc   collapse and  lambda s      join s split     or  lambda s  s      print   n  join    s  s                          method ljust spacing                         processFunc str getattr object  method    doc                           for method in methodList    if   name         main         print help   doc

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Python has a strong set of introspection features    Take a look at the following built-in functions    type   dir   id   getattr   hasattr   globals   locals   callable     type   and dir   are particularly useful for inspecting the type of an object and its set of attributes  respectively

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You can list the attributes of a object with dir   in the shell    gt  gt  gt  dir object        class        delattr        doc        format        getattribute        hash        init        new        reduce        reduce ex        repr        setattr        sizeof        str        subclasshook       Of course  there is also the inspect module  http   docs python org library inspect html module-inspect

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In addition if you want to look inside list and dictionaries  you can use pprint

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import pprint  pprint pprint obj   dict      or  pprint pprint vars obj

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While pprint has been mentioned already by others I d like to add some context      The pprint module provides a capability to    pretty-print    arbitrary   Python data structures in a form which can be used as input to the   interpreter  If the formatted structures include objects which are not   fundamental Python types  the representation may not be loadable  This   may be the case if objects such as files  sockets  classes  or   instances are included  as well as many other built-in objects which   are not representable as Python constants    pprint might be in high-demand by developers with a PHP background who are looking for an alternative to var dump     Objects with a dict attribute can be dumped nicely using pprint   mixed with vars    which returns the   dict   attribute for a module  class  instance  etc    from pprint import pprint pprint vars your object     So  no need for a loop     To dump all variables contained in the global or local scope simply use   pprint globals    pprint locals      locals   shows variables defined in a function  It s also useful to access functions with their corresponding name as a string key  among other usages   locals    foo       foo   globals    foo       foo     Similarly  using dir   to see the contents of a module  or the attributes of an object   And there is still more

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pprint and dir together work great

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Try ppretty  from ppretty import ppretty   class A object       s   5      def   init   self           self  p   8       property     def foo self           return range 10    print ppretty A    indent         depth 2  width 30  seq length 6                show protected True  show private False  show static True                show properties True  show address True    Output     main   A at 0x1debd68L        p   8       foo    0  1  2       7  8  9        s   5

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In Python 3 8  you can print out the contents of an object by using the   dict    For example  class Person       pass  person   Person       set attributes person first    Oyinda  person last    David      to see the content of the object print person   dict         quot first quot    quot Oyinda quot    quot last quot    quot David quot

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If you re interested in a GUI for this  take a look at objbrowser  It uses the inspect module from the Python standard library for the object introspection underneath

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There is a python code library build just for this purpose  inspect  Introduced in Python 2 7

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vars obj  returns the attributes of an object

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Two great tools for inspecting code are    IPython  A python terminal that allows you to inspect using tab completion  Eclipse with the PyDev plugin  It has an excellent debugger that allows you to break at a given spot and inspect objects by browsing all variables as a tree   You can even use the embedded terminal to try code at that spot or type the object and press     to have it give code hints for you

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I m surprised no one s mentioned help yet   In  1   def foo                 foo            In  2   help foo  Help on function foo in module   main     foo       foo    Help lets you read the docstring and get an idea of what attributes a class might have  which is pretty helpful

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If this is for exploration to see what s going on  I d recommend looking at IPython   This adds various shortcuts to obtain an objects documentation  properties and even source code   For instance appending a     to a function will give the help for the object  effectively a shortcut for  help obj    wheras using two   s   func     will display the sourcecode if it is available   There are also a lot of additional conveniences  like tab completion  pretty printing of results  result history etc  that make it very handy for this sort of exploratory programming   For more programmatic use of introspection  the basic builtins like dir    vars    getattr etc will be useful  but it is well worth your time to check out the inspect module   To fetch the source of a function  use  inspect getsource   eg  applying it to itself    gt  gt  gt  print inspect getsource inspect getsource  def getsource object          Return the text of the source code for an object       The argument may be a module  class  method  function  traceback  frame      or code object   The source code is returned as a single string   An     IOError is raised if the source code cannot be retrieved         lines  lnum   getsourcelines object      return string join lines        inspect getargspec is also frequently useful if you re dealing with wrapping or manipulating functions  as it will give the names and default values of function parameters

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Others have already mentioned the dir   built-in which sounds like what you re looking for  but here s another good tip   Many libraries -- including most of the standard library -- are distributed in source form   Meaning you can pretty easily read the source code directly   The trick is in finding it  for example    gt  gt  gt  import string  gt  gt  gt  string   file     usr lib python2 5 string pyc    The   pyc file is compiled  so remove the trailing  c  and open up the uncompiled   py file in your favorite editor or file viewer    usr lib python2 5 string py   I ve found this incredibly useful for discovering things like which exceptions are raised from a given API   This kind of detail is rarely well-documented in the Python world

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Try using   print object stringify       where object is the variable name of the object you are trying to inspect    This prints out a nicely formatted and tabbed output showing all the hierarchy of keys and values in the object   NOTE  This works in python3  Not sure if it works in earlier versions  UPDATE  This doesn t work on all types of objects  If you encounter one of those types  like a Request object   use one of the following instead    dir object      or   import pprint then  pprint pprint object   dict

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If you want to look inside a live object  then python s inspect module is a good answer   In general  it works for getting the source code of functions that are defined in a source file somewhere on disk  If you want to get the source of live functions and lambdas that were defined in the interpreter  you can use dill source getsource from dill  It also can get the code for from bound or unbound class methods and functions defined in curries    however  you might not be able to compile that code without the enclosing object s code    gt  gt  gt  from dill source import getsource  gt  gt  gt    gt  gt  gt  def add x y         return x y       gt  gt  gt  squared   lambda x x  2  gt  gt  gt    gt  gt  gt  print getsource add  def add x y     return x y   gt  gt  gt  print getsource squared  squared   lambda x x  2   gt  gt  gt    gt  gt  gt  class Foo object         def bar self  x           return x x x       gt  gt  gt  f   Foo    gt  gt  gt    gt  gt  gt  print getsource f bar  def bar self  x       return x x x   gt  gt  gt

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If you are interested to see the source code of the function corresponding to the object myobj  you can type in iPython or Jupyter Notebook   myobj

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object   dict

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If you want to look at parameters and methods  as others have pointed out you may well use pprint or dir    If you want to see the actual value of the contents  you can do  object   dict

[python] How do I look inside a Python object?

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