How do I parse a string to a float or int

Question

In Python  how can I parse a numeric string like  545 2222  to its corresponding float value  545 2222  Or parse the string  31  to an integer  31   I just want to know how to parse a float str to a float  and  separately  an int str to an int

User · Answer

Localization and commas

You should consider the possibility of commas in the string representation of a number, for cases like float("545,545.2222") which throws an exception. Instead, use methods in locale to convert the strings to numbers and interpret commas correctly. The locale.atof method converts to a float in one step once the locale has been set for the desired number convention.

Example 1 -- United States number conventions

In the United States and the UK, commas can be used as a thousands separator. In this example with American locale, the comma is handled properly as a separator:

>>> import locale
>>> a = u'545,545.2222'
>>> locale.setlocale(locale.LC_ALL, 'en_US.UTF-8')
'en_US.UTF-8'
>>> locale.atof(a)
545545.2222
>>> int(locale.atof(a))
545545
>>>

Example 2 -- European number conventions

In the majority of countries of the world, commas are used for decimal marks instead of periods. In this example with French locale, the comma is correctly handled as a decimal mark:

>>> import locale
>>> b = u'545,2222'
>>> locale.setlocale(locale.LC_ALL, 'fr_FR')
'fr_FR'
>>> locale.atof(b)
545.2222

The method locale.atoi is also available, but the argument should be an integer.

User · Answer

for number and char together   string for int    quot 498 results should get quot  string for float    quot 498 45645765 results should get quot   first import re   import re    for get integer part   print int re search r  d    string for int  group      498    for get float part   print float re search r  d    d    string for float  group      498 45645765  for easy model   value1    quot 10 quot  value2    quot 10 2 quot  print int value1    10 print float value2    10 2

User · Answer

Pass your string to this function    def string to number str     if     in str       try        res   float str      except        res   str     elif str isdigit         res   int str    else      res   str   return res    It will return int  float or string depending on what was passed    string that is an int  print type string to number  124      lt class  int  gt    string that is a float  print type string to number  12 4      lt class  float  gt    string that is a string  print type string to number  hello      lt class  str  gt    string that looks like a float  print type string to number  hel lo      lt class  str  gt

User · Answer

I use this function for that  import ast  def parse str s      try        return ast literal eval str s      except        return   It will convert the string to its type  value   parse str  1      Returns Integer value   parse str  1 5      Returns Float

User · Answer

I am surprised nobody mentioned regex because sometimes string must be prepared and normalized before casting to number  import re def parseNumber value  as int False       try          number   float re sub      - d        value           if as int              return int number   0 5          else              return number     except ValueError          return float  nan      or None if you wish   usage   parseNumber  13 345    gt  13345 0  parseNumber  - 123 000    gt  -123000 0  parseNumber  99999 n    gt  99999 0   and by the way  something to verify you have a number   import numbers def is number value       return isinstance value  numbers Number        will work with int  float  long  Decimal

User · Answer

This is a corrected version of  https   stackoverflow com a 33017514 5973334  This will try to parse a string and return either int or float depending on what the string represents  It might rise parsing exceptions or have some unexpected behaviour     def get int or float v           number as float   float v          number as int   int number as float          return number as int if number as float    number as int else          number as float

User · Answer

The question seems a little bit old  But let me suggest a function  parseStr  which makes something similar  that is  returns integer or float and if a given ASCII string cannot be converted to none of them it returns it untouched  The code of course might be adjusted to do only what you want       gt  gt  gt  import string     gt  gt  gt  parseStr   lambda x  x isalpha   and x or x isdigit   and                               int x  or x isalnum   and x or                               len set string punctuation  intersection x      1 and                               x count         1 and float x  or x     gt  gt  gt  parseStr  123      123     gt  gt  gt  parseStr  123 3      123 3     gt  gt  gt  parseStr  3HC1       3HC1      gt  gt  gt  parseStr  12 e5      1200000 0     gt  gt  gt  parseStr  12 5       12 5      gt  gt  gt  parseStr  12 2 2       12 2 2

User · Answer

def get int or float v       number as float   float v      number as int   int number as float      return number as int if number as float    number as int else number as float

User · Answer

float  545 2222   and int float  545 2222

User · Answer

Python method to check if a string is a float   def is float value     try      float value      return True   except      return False   A longer and more accurate name for this function could be  is convertible to float value   What is  and is not a float in Python may surprise you   val                   is float val  Note --------------------  ----------   --------------------------------                       False        Blank string  127                  True         Passed string True                  True         Pure sweet Truth  True                 False        Vile contemptible lie False                 True         So false it becomes true  123 456              True         Decimal        -127           True         Spaces trimmed   t n12 r n           True         whitespace ignored  NaN                  True         Not a number  NaNanananaBATMAN     False        I am Batman  -iNF                 True         Negative infinity  123 E4               True         Exponential notation   1                   True         mantissa only  1 234                False        Commas gtfo u  x30                True         Unicode is fine   NULL                 False        Null is not special 0x3fade               True         Hexadecimal  6e7777777777777      True         Shrunk to infinity  1 797693e 308        True         This is max value  infinity             True         Same as inf  infinityandBEYOND    False        Extra characters wreck it  12 34 56             False        Only one dot allowed u                    False        Japanese  4  is not a float    56                  False        Pound sign  56                   False        Percent of what   0E0                  True         Exponential  move dot 0 places 0  0                  True         0   0  Exponentiation  -5e-5                True         Raise to a negative number   1e1                 True         Plus is OK with exponent   1e1 5               False        Fancy exponent not interpreted   1e1 3               False        No decimals in exponent  - 1                  False        Make up your mind   1                   False        Parenthesis is bad   You think you know what numbers are  You are not so good as you think  Not big surprise   Don t use this code on life-critical software   Catching broad exceptions this way  killing canaries and gobbling the exception creates a tiny chance that a valid float as string will return false   The float      line of code can failed for any of a thousand reasons that have nothing to do with the contents of the string   But if you re writing life-critical software in a duck-typing prototype language like Python  then you ve got much larger problems

User · Answer

This is a function which will convert any object  not just str  to int or float  based on if the actual string supplied looks like int or float  Further if it s an object which has both   float and   int   methods  it defaults to using   float    def conv to num x  num type  asis           Converts an object to a number if possible      num type  int  float   asis      Defaults to floating point in case of ambiguity              import numbers      is num  is str  is other    False  3      if isinstance x  numbers Number           is num   True     elif isinstance x  str           is str   True      is other   not any  is num  is str        if is num          res   x     elif is str          is float  is int  is char    False  3         try              res   float x              if     in x                  is float   True             else                  is int   True         except ValueError              res   x             is char   True      else          if num type     asis               funcs    int  float          else              funcs    num type           for func in funcs              try                  res   func x                  break             except TypeError                  continue         else              res   x

User · Answer

The YAML parser can help you figure out what datatype your string is  Use yaml load    and then you can use type result  to test for type    gt  gt  gt  import yaml   gt  gt  gt  a    545 2222   gt  gt  gt  result   yaml load a   gt  gt  gt  result 545 22220000000004  gt  gt  gt  type result   lt type  float  gt    gt  gt  gt  b    31   gt  gt  gt  result   yaml load b   gt  gt  gt  result 31  gt  gt  gt  type result   lt type  int  gt    gt  gt  gt  c    HI   gt  gt  gt  result   yaml load c   gt  gt  gt  result  HI   gt  gt  gt  type result   lt type  str  gt

User · Answer

float x  if     in x else int x

User · Answer

I am surprised nobody mentioned regex because sometimes string must be prepared and normalized before casting to number  import re def parseNumber value  as int False       try          number   float re sub      - d        value           if as int              return int number   0 5          else              return number     except ValueError          return float  nan      or None if you wish   usage   parseNumber  13 345    gt  13345 0  parseNumber  - 123 000    gt  -123000 0  parseNumber  99999 n    gt  99999 0   and by the way  something to verify you have a number   import numbers def is number value       return isinstance value  numbers Number        will work with int  float  long  Decimal

User · Answer

for number and char together   string for int    quot 498 results should get quot  string for float    quot 498 45645765 results should get quot   first import re   import re    for get integer part   print int re search r  d    string for int  group      498    for get float part   print float re search r  d    d    string for float  group      498 45645765  for easy model   value1    quot 10 quot  value2    quot 10 2 quot  print int value1    10 print float value2    10 2

User · Answer

def num s          num s      num 3  num 3 7 -- gt 3     num  3  -- gt 3  num  3 7  -- gt 3 7     num  3 700  -- gt ValueError     num  3a   num  a3   -- gt ValueError     num  3e4   -- gt  30000 0             try          return int s      except ValueError          try              return float s          except ValueError              raise ValueError  argument is not a string of number

User · Answer

Here s another interpretation of your question  hint  it s vague   It s possible you re looking for something like this   def parseIntOrFloat  aString        return eval  aString     It works like this      gt  gt  gt  parseIntOrFloat  545 2222   545 22220000000004  gt  gt  gt  parseIntOrFloat  545   545     Theoretically  there s an injection vulnerability  The string could  for example be  import os  os abort     Without any background on where the string comes from  however  the possibility is theoretical speculation   Since the question is vague  it s not at all clear if this vulnerability actually exists or not

User · Answer

If you aren t averse to third-party modules  you could check out the fastnumbers module  It provides a function called fast real that does exactly what this question is asking for and does it faster than a pure-Python implementation    gt  gt  gt  from fastnumbers import fast real  gt  gt  gt  fast real  545 2222   545 2222  gt  gt  gt  type fast real  545 2222    float  gt  gt  gt  fast real  31   31  gt  gt  gt  type fast real  31    int

User · Answer

By using int and float methods we can convert a string to integer and floats   s  45 8  print float s    y  67  print int y

User · Answer

def num s       try          return int s      except ValueError          return float s

User · Answer

You need to take into account rounding to do this properly   I e  int 5 1     5      int 5 6     5  -- wrong  should be 6 so we do int 5 6   0 5     6  def convert n       try          return int n      except ValueError          return float n   0 5

User · Answer

Users codelogic and harley are correct  but keep in mind if you know the string is an integer  for example  545  you can call int  545   without first casting to float   If your strings are in a list  you could use the map function as well     gt  gt  gt  x     545 0    545 6    999 2    gt  gt  gt  map float  x   545 0  545 60000000000002  999 20000000000005   gt  gt  gt    It is only good if they re all the same type

User · Answer

Localization and commas

You should consider the possibility of commas in the string representation of a number, for cases like float("545,545.2222") which throws an exception. Instead, use methods in locale to convert the strings to numbers and interpret commas correctly. The locale.atof method converts to a float in one step once the locale has been set for the desired number convention.

Example 1 -- United States number conventions

In the United States and the UK, commas can be used as a thousands separator. In this example with American locale, the comma is handled properly as a separator:

>>> import locale
>>> a = u'545,545.2222'
>>> locale.setlocale(locale.LC_ALL, 'en_US.UTF-8')
'en_US.UTF-8'
>>> locale.atof(a)
545545.2222
>>> int(locale.atof(a))
545545
>>>

Example 2 -- European number conventions

In the majority of countries of the world, commas are used for decimal marks instead of periods. In this example with French locale, the comma is correctly handled as a decimal mark:

>>> import locale
>>> b = u'545,2222'
>>> locale.setlocale(locale.LC_ALL, 'fr_FR')
'fr_FR'
>>> locale.atof(b)
545.2222

The method locale.atoi is also available, but the argument should be an integer.

User · Answer

gt  gt  gt  a    545 2222   gt  gt  gt  float a  545 22220000000004  gt  gt  gt  int float a   545

User · Answer

float  545 2222   and int float  545 2222

User · Answer

def num s          num s      num 3  num 3 7 -- gt 3     num  3  -- gt 3  num  3 7  -- gt 3 7     num  3 700  -- gt ValueError     num  3a   num  a3   -- gt ValueError     num  3e4   -- gt  30000 0             try          return int s      except ValueError          try              return float s          except ValueError              raise ValueError  argument is not a string of number

User · Answer

I use this function for that  import ast  def parse str s      try        return ast literal eval str s      except        return   It will convert the string to its type  value   parse str  1      Returns Integer value   parse str  1 5      Returns Float

User · Answer

float  545 2222   and int float  545 2222

User · Answer

Users codelogic and harley are correct  but keep in mind if you know the string is an integer  for example  545  you can call int  545   without first casting to float   If your strings are in a list  you could use the map function as well     gt  gt  gt  x     545 0    545 6    999 2    gt  gt  gt  map float  x   545 0  545 60000000000002  999 20000000000005   gt  gt  gt    It is only good if they re all the same type

User · Answer

To typecast in python use the constructor funtions of the type  passing the string  or whatever value you are trying to cast  as a parameter   For example    gt  gt  gt float  23 333      23 333   Behind the scenes  python is calling the objects   float   method  which should return a float representation of the parameter  This is especially powerful  as you can define your own types  using classes  with a   float   method so that it can be casted into a float using float myobject

User · Answer

Use   def num s       try          for each in s              yield int each      except ValueError          yield float each  a   num   123 55   345   44    print a next   print a next     This is the most Pythonic way I could come up with

User · Answer

Here s another interpretation of your question  hint  it s vague   It s possible you re looking for something like this   def parseIntOrFloat  aString        return eval  aString     It works like this      gt  gt  gt  parseIntOrFloat  545 2222   545 22220000000004  gt  gt  gt  parseIntOrFloat  545   545     Theoretically  there s an injection vulnerability  The string could  for example be  import os  os abort     Without any background on where the string comes from  however  the possibility is theoretical speculation   Since the question is vague  it s not at all clear if this vulnerability actually exists or not

User · Answer

By using int and float methods we can convert a string to integer and floats   s  45 8  print float s    y  67  print int y

User · Answer

Here s another interpretation of your question  hint  it s vague   It s possible you re looking for something like this   def parseIntOrFloat  aString        return eval  aString     It works like this      gt  gt  gt  parseIntOrFloat  545 2222   545 22220000000004  gt  gt  gt  parseIntOrFloat  545   545     Theoretically  there s an injection vulnerability  The string could  for example be  import os  os abort     Without any background on where the string comes from  however  the possibility is theoretical speculation   Since the question is vague  it s not at all clear if this vulnerability actually exists or not

User · Answer

a   int float a   if int float a      float a  else float a

User · Answer

gt  gt  gt  a    545 2222   gt  gt  gt  float a  545 22220000000004  gt  gt  gt  int float a   545

User · Answer

In Python  how can I parse a numeric string like  545 2222  to its corresponding float value  542 2222  Or parse the string  31  to an integer  31    I just want to know how to parse a float string to a float  and  separately  an int string to an int    It s good that you ask to do these separately  If you re mixing them  you may be setting yourself up for problems later  The simple answer is    545 2222  to float    gt  gt  gt  float  545 2222   545 2222    31  to an integer    gt  gt  gt  int  31   31   Other conversions  ints to and from strings and literals   Conversions from various bases  and you should know the base in advance  10 is the default   Note you can prefix them with what Python expects for its literals  see below  or remove the prefix    gt  gt  gt  int  0b11111   2  31  gt  gt  gt  int  11111   2  31  gt  gt  gt  int  0o37   8  31  gt  gt  gt  int  37   8  31  gt  gt  gt  int  0x1f   16  31  gt  gt  gt  int  1f   16  31   If you don t know the base in advance  but you do know they will have the correct prefix  Python can infer this for you if you pass 0 as the base    gt  gt  gt  int  0b11111   0  31  gt  gt  gt  int  0o37   0  31  gt  gt  gt  int  0x1f   0  31   Non-Decimal  i e  Integer  Literals from other Bases  If your motivation is to have your own code clearly represent hard-coded specific values  however  you may not need to convert from the bases - you can let Python do it for you automatically with the correct syntax   You can use the apropos prefixes to get automatic conversion to integers with the following literals  These are valid for Python 2 and 3   Binary  prefix 0b   gt  gt  gt  0b11111 31   Octal  prefix 0o   gt  gt  gt  0o37 31   Hexadecimal  prefix 0x   gt  gt  gt  0x1f 31   This can be useful when describing binary flags  file permissions in code  or hex values for colors - for example  note no quotes    gt  gt  gt  0b10101   binary flags 21  gt  gt  gt  0o755   read  write  execute perms for owner  read  amp  ex for group  amp  others 493  gt  gt  gt  0xffffff   the color  white  max values for red  green  and blue 16777215   Making ambiguous Python 2 octals compatible with Python 3  If you see an integer that starts with a 0  in Python 2  this is  deprecated  octal syntax    gt  gt  gt  037 31   It is bad because it looks like the value should be 37  So in Python 3  it now raises a SyntaxError    gt  gt  gt  037   File   lt stdin gt    line 1     037         SyntaxError  invalid token   Convert your Python 2 octals to octals that work in both 2 and 3 with the 0o prefix    gt  gt  gt  0o37 31

User · Answer

Users codelogic and harley are correct  but keep in mind if you know the string is an integer  for example  545  you can call int  545   without first casting to float   If your strings are in a list  you could use the map function as well     gt  gt  gt  x     545 0    545 6    999 2    gt  gt  gt  map float  x   545 0  545 60000000000002  999 20000000000005   gt  gt  gt    It is only good if they re all the same type

User · Answer

Use    gt  gt  gt  str float    545 2222   gt  gt  gt  float str float  545 2222  gt  gt  gt  type      Check its type  lt type  float  gt    gt  gt  gt  str int    31   gt  gt  gt  int str int  31  gt  gt  gt  type      Check its type  lt type  int  gt

User · Answer

Use    gt  gt  gt  str float    545 2222   gt  gt  gt  float str float  545 2222  gt  gt  gt  type      Check its type  lt type  float  gt    gt  gt  gt  str int    31   gt  gt  gt  int str int  31  gt  gt  gt  type      Check its type  lt type  int  gt

User · Answer

float x  if     in x else int x

User · Answer

Users codelogic and harley are correct  but keep in mind if you know the string is an integer  for example  545  you can call int  545   without first casting to float   If your strings are in a list  you could use the map function as well     gt  gt  gt  x     545 0    545 6    999 2    gt  gt  gt  map float  x   545 0  545 60000000000002  999 20000000000005   gt  gt  gt    It is only good if they re all the same type

User · Answer

Handles hex  octal  binary  decimal  and float  This solution will handle all of the string conventions for numbers  all that I know about    def to number n           Convert any number representation to a number      This covers  float  decimal  hex  and octal numbers               try          return int str n   0      except          try                python 3 doesn t accept  010  as a valid octal   You must use the                0o  prefix             return int  0o    n  0          except              return float n    This test case output illustrates what I m talking about                            CAPTURED OUTPUT                           to number 3735928559      3735928559    3735928559 to number  0xFEEDFACE     4277009102    4277009102 to number  0x0                     0             0 to number 100                    100           100 to number  42                     42            42 to number 8                        8             8 to number  0o20                   16            16 to number  020                    16            16 to number 3 14                  3 14          3 14 to number  2 72                 2 72          2 72 to number  1e3                1000 0          1000 to number 0 001                0 001         0 001 to number  0xA                    10            10 to number  012                    10            10 to number  0o12                   10            10 to number  0b01010                10            10 to number  10                     10            10 to number  10 0                 10 0            10 to number  1e1                  10 0            10   Here is the test   class test to number unittest TestCase        def test hex self             All of the following should be converted to an integer                   values                                  HEX                    ----------------------                    Input         Expected                    ----------------------                  0xDEADBEEF    3735928559     Hex                   0xFEEDFACE   4277009102     Hex                   0x0                   0     Hex                            Decimals                    ----------------------                    Input         Expected                    ----------------------                  100                  100     Decimal                   42                   42     Decimal                          values                                Octals                    ----------------------                    Input         Expected                    ----------------------                  0o10                   8     Octal                   0o20                 16     Octal                   020                  16     Octal                         values                                Floats                    ----------------------                    Input         Expected                    ----------------------                  3 14                3 14     Float                   2 72               2 72     Float                   1e3                1000     Float                  1e-3               0 001     Float                        values                                All ints                    ----------------------                    Input         Expected                    ----------------------                   0xA                  10                      012                  10                      0o12                 10                      0b01010              10                      10                   10                      10 0                 10                      1e1                  10                           for  input  expected in values              value   to number  input               if isinstance  input  str                   cmd    to number        format  input              else                  cmd    to number      format  input               print    23      10       10   format cmd  value  expected               self assertEqual value  expected

User · Answer

a   int float a   if int float a      float a  else float a

User · Answer

def num s       try          return int s      except ValueError          return float s

User · Answer

def get int or float v       number as float   float v      number as int   int number as float      return number as int if number as float    number as int else number as float

User · Answer

gt  gt  gt  a    545 2222   gt  gt  gt  float a  545 22220000000004  gt  gt  gt  int float a   545

User · Answer

This is another method which deserves to be mentioned here  ast literal eval      This can be used for safely evaluating strings containing Python expressions from untrusted sources without the need to parse the values oneself    That is  a safe  eval    gt  gt  gt  import ast  gt  gt  gt  ast literal eval  545 2222   545 2222  gt  gt  gt  ast literal eval  31   31

User · Answer

Use   def num s       try          for each in s              yield int each      except ValueError          yield float each  a   num   123 55   345   44    print a next   print a next     This is the most Pythonic way I could come up with

User · Answer

Python method to check if a string is a float   def is float value     try      float value      return True   except      return False   A longer and more accurate name for this function could be  is convertible to float value   What is  and is not a float in Python may surprise you   val                   is float val  Note --------------------  ----------   --------------------------------                       False        Blank string  127                  True         Passed string True                  True         Pure sweet Truth  True                 False        Vile contemptible lie False                 True         So false it becomes true  123 456              True         Decimal        -127           True         Spaces trimmed   t n12 r n           True         whitespace ignored  NaN                  True         Not a number  NaNanananaBATMAN     False        I am Batman  -iNF                 True         Negative infinity  123 E4               True         Exponential notation   1                   True         mantissa only  1 234                False        Commas gtfo u  x30                True         Unicode is fine   NULL                 False        Null is not special 0x3fade               True         Hexadecimal  6e7777777777777      True         Shrunk to infinity  1 797693e 308        True         This is max value  infinity             True         Same as inf  infinityandBEYOND    False        Extra characters wreck it  12 34 56             False        Only one dot allowed u                    False        Japanese  4  is not a float    56                  False        Pound sign  56                   False        Percent of what   0E0                  True         Exponential  move dot 0 places 0  0                  True         0   0  Exponentiation  -5e-5                True         Raise to a negative number   1e1                 True         Plus is OK with exponent   1e1 5               False        Fancy exponent not interpreted   1e1 3               False        No decimals in exponent  - 1                  False        Make up your mind   1                   False        Parenthesis is bad   You think you know what numbers are  You are not so good as you think  Not big surprise   Don t use this code on life-critical software   Catching broad exceptions this way  killing canaries and gobbling the exception creates a tiny chance that a valid float as string will return false   The float      line of code can failed for any of a thousand reasons that have nothing to do with the contents of the string   But if you re writing life-critical software in a duck-typing prototype language like Python  then you ve got much larger problems

User · Answer

gt  gt  gt  a    545 2222   gt  gt  gt  float a  545 22220000000004  gt  gt  gt  int float a   545

User · Answer

This is a function which will convert any object  not just str  to int or float  based on if the actual string supplied looks like int or float  Further if it s an object which has both   float and   int   methods  it defaults to using   float    def conv to num x  num type  asis           Converts an object to a number if possible      num type  int  float   asis      Defaults to floating point in case of ambiguity              import numbers      is num  is str  is other    False  3      if isinstance x  numbers Number           is num   True     elif isinstance x  str           is str   True      is other   not any  is num  is str        if is num          res   x     elif is str          is float  is int  is char    False  3         try              res   float x              if     in x                  is float   True             else                  is int   True         except ValueError              res   x             is char   True      else          if num type     asis               funcs    int  float          else              funcs    num type           for func in funcs              try                  res   func x                  break             except TypeError                  continue         else              res   x

User · Answer

def num s       try          return int s      except ValueError          return float s

User · Answer

float  545 2222   and int float  545 2222

User · Answer

If you aren t averse to third-party modules  you could check out the fastnumbers module  It provides a function called fast real that does exactly what this question is asking for and does it faster than a pure-Python implementation    gt  gt  gt  from fastnumbers import fast real  gt  gt  gt  fast real  545 2222   545 2222  gt  gt  gt  type fast real  545 2222    float  gt  gt  gt  fast real  31   31  gt  gt  gt  type fast real  31    int

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In Python  how can I parse a numeric string like  545 2222  to its corresponding float value  542 2222  Or parse the string  31  to an integer  31    I just want to know how to parse a float string to a float  and  separately  an int string to an int    It s good that you ask to do these separately  If you re mixing them  you may be setting yourself up for problems later  The simple answer is    545 2222  to float    gt  gt  gt  float  545 2222   545 2222    31  to an integer    gt  gt  gt  int  31   31   Other conversions  ints to and from strings and literals   Conversions from various bases  and you should know the base in advance  10 is the default   Note you can prefix them with what Python expects for its literals  see below  or remove the prefix    gt  gt  gt  int  0b11111   2  31  gt  gt  gt  int  11111   2  31  gt  gt  gt  int  0o37   8  31  gt  gt  gt  int  37   8  31  gt  gt  gt  int  0x1f   16  31  gt  gt  gt  int  1f   16  31   If you don t know the base in advance  but you do know they will have the correct prefix  Python can infer this for you if you pass 0 as the base    gt  gt  gt  int  0b11111   0  31  gt  gt  gt  int  0o37   0  31  gt  gt  gt  int  0x1f   0  31   Non-Decimal  i e  Integer  Literals from other Bases  If your motivation is to have your own code clearly represent hard-coded specific values  however  you may not need to convert from the bases - you can let Python do it for you automatically with the correct syntax   You can use the apropos prefixes to get automatic conversion to integers with the following literals  These are valid for Python 2 and 3   Binary  prefix 0b   gt  gt  gt  0b11111 31   Octal  prefix 0o   gt  gt  gt  0o37 31   Hexadecimal  prefix 0x   gt  gt  gt  0x1f 31   This can be useful when describing binary flags  file permissions in code  or hex values for colors - for example  note no quotes    gt  gt  gt  0b10101   binary flags 21  gt  gt  gt  0o755   read  write  execute perms for owner  read  amp  ex for group  amp  others 493  gt  gt  gt  0xffffff   the color  white  max values for red  green  and blue 16777215   Making ambiguous Python 2 octals compatible with Python 3  If you see an integer that starts with a 0  in Python 2  this is  deprecated  octal syntax    gt  gt  gt  037 31   It is bad because it looks like the value should be 37  So in Python 3  it now raises a SyntaxError    gt  gt  gt  037   File   lt stdin gt    line 1     037         SyntaxError  invalid token   Convert your Python 2 octals to octals that work in both 2 and 3 with the 0o prefix    gt  gt  gt  0o37 31

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The question seems a little bit old  But let me suggest a function  parseStr  which makes something similar  that is  returns integer or float and if a given ASCII string cannot be converted to none of them it returns it untouched  The code of course might be adjusted to do only what you want       gt  gt  gt  import string     gt  gt  gt  parseStr   lambda x  x isalpha   and x or x isdigit   and                               int x  or x isalnum   and x or                               len set string punctuation  intersection x      1 and                               x count         1 and float x  or x     gt  gt  gt  parseStr  123      123     gt  gt  gt  parseStr  123 3      123 3     gt  gt  gt  parseStr  3HC1       3HC1      gt  gt  gt  parseStr  12 e5      1200000 0     gt  gt  gt  parseStr  12 5       12 5      gt  gt  gt  parseStr  12 2 2       12 2 2

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float x  if     in x else int x

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You need to take into account rounding to do this properly   I e  int 5 1     5      int 5 6     5  -- wrong  should be 6 so we do int 5 6   0 5     6  def convert n       try          return int n      except ValueError          return float n   0 5

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This is a corrected version of  https   stackoverflow com a 33017514 5973334  This will try to parse a string and return either int or float depending on what the string represents  It might rise parsing exceptions or have some unexpected behaviour     def get int or float v           number as float   float v          number as int   int number as float          return number as int if number as float    number as int else          number as float

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The YAML parser can help you figure out what datatype your string is  Use yaml load    and then you can use type result  to test for type    gt  gt  gt  import yaml   gt  gt  gt  a    545 2222   gt  gt  gt  result   yaml load a   gt  gt  gt  result 545 22220000000004  gt  gt  gt  type result   lt type  float  gt    gt  gt  gt  b    31   gt  gt  gt  result   yaml load b   gt  gt  gt  result 31  gt  gt  gt  type result   lt type  int  gt    gt  gt  gt  c    HI   gt  gt  gt  result   yaml load c   gt  gt  gt  result  HI   gt  gt  gt  type result   lt type  str  gt

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Handles hex  octal  binary  decimal  and float  This solution will handle all of the string conventions for numbers  all that I know about    def to number n           Convert any number representation to a number      This covers  float  decimal  hex  and octal numbers               try          return int str n   0      except          try                python 3 doesn t accept  010  as a valid octal   You must use the                0o  prefix             return int  0o    n  0          except              return float n    This test case output illustrates what I m talking about                            CAPTURED OUTPUT                           to number 3735928559      3735928559    3735928559 to number  0xFEEDFACE     4277009102    4277009102 to number  0x0                     0             0 to number 100                    100           100 to number  42                     42            42 to number 8                        8             8 to number  0o20                   16            16 to number  020                    16            16 to number 3 14                  3 14          3 14 to number  2 72                 2 72          2 72 to number  1e3                1000 0          1000 to number 0 001                0 001         0 001 to number  0xA                    10            10 to number  012                    10            10 to number  0o12                   10            10 to number  0b01010                10            10 to number  10                     10            10 to number  10 0                 10 0            10 to number  1e1                  10 0            10   Here is the test   class test to number unittest TestCase        def test hex self             All of the following should be converted to an integer                   values                                  HEX                    ----------------------                    Input         Expected                    ----------------------                  0xDEADBEEF    3735928559     Hex                   0xFEEDFACE   4277009102     Hex                   0x0                   0     Hex                            Decimals                    ----------------------                    Input         Expected                    ----------------------                  100                  100     Decimal                   42                   42     Decimal                          values                                Octals                    ----------------------                    Input         Expected                    ----------------------                  0o10                   8     Octal                   0o20                 16     Octal                   020                  16     Octal                         values                                Floats                    ----------------------                    Input         Expected                    ----------------------                  3 14                3 14     Float                   2 72               2 72     Float                   1e3                1000     Float                  1e-3               0 001     Float                        values                                All ints                    ----------------------                    Input         Expected                    ----------------------                   0xA                  10                      012                  10                      0o12                 10                      0b01010              10                      10                   10                      10 0                 10                      1e1                  10                           for  input  expected in values              value   to number  input               if isinstance  input  str                   cmd    to number        format  input              else                  cmd    to number      format  input               print    23      10       10   format cmd  value  expected               self assertEqual value  expected

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This is another method which deserves to be mentioned here  ast literal eval      This can be used for safely evaluating strings containing Python expressions from untrusted sources without the need to parse the values oneself    That is  a safe  eval    gt  gt  gt  import ast  gt  gt  gt  ast literal eval  545 2222   545 2222  gt  gt  gt  ast literal eval  31   31

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To typecast in python use the constructor funtions of the type  passing the string  or whatever value you are trying to cast  as a parameter   For example    gt  gt  gt float  23 333      23 333   Behind the scenes  python is calling the objects   float   method  which should return a float representation of the parameter  This is especially powerful  as you can define your own types  using classes  with a   float   method so that it can be casted into a float using float myobject

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Here s another interpretation of your question  hint  it s vague   It s possible you re looking for something like this   def parseIntOrFloat  aString        return eval  aString     It works like this      gt  gt  gt  parseIntOrFloat  545 2222   545 22220000000004  gt  gt  gt  parseIntOrFloat  545   545     Theoretically  there s an injection vulnerability  The string could  for example be  import os  os abort     Without any background on where the string comes from  however  the possibility is theoretical speculation   Since the question is vague  it s not at all clear if this vulnerability actually exists or not

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float x  if     in x else int x

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def num s       try          return int s      except ValueError          return float s

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Pass your string to this function    def string to number str     if     in str       try        res   float str      except        res   str     elif str isdigit         res   int str    else      res   str   return res    It will return int  float or string depending on what was passed    string that is an int  print type string to number  124      lt class  int  gt    string that is a float  print type string to number  12 4      lt class  float  gt    string that is a string  print type string to number  hello      lt class  str  gt    string that looks like a float  print type string to number  hel lo      lt class  str  gt

[python] How do I parse a string to a float or int?

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