How to convert strings into integers in Python

Question

I have a tuple of tuples from a MySQL query like this   T1      13    17    18    21    32            07    11    13    14    28            01    05    06    08    15    16      I d like to convert all the string elements into integers and put them back into a list of lists   T2     13  17  18  21  32    7  11  13  14  28    1  5  6  8  15  16     I tried to achieve it with eval but didn t get any decent result yet

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In Python 3 5 1 things like these work   c   input  Enter number    print  int float c    print  round float c      and  Enter number   4 7 4 5   George

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Using list comprehensions   t2    map int  list l   for l in t1

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See this function  def parse int s       try          res   int eval str s            if type res     int              return res     except          return   Then  val   parse int  10      Return 10 val   parse int  0      Return 0 val   parse int  10 5      Return 10 val   parse int  0 0      Return 0 val   parse int  Ten      Return None   You can also check  if val    None     True if input value can not be converted     pass    Note  Don t use  if not val

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Try this   x    1    x is a string because it has quotes around it  but it has a number in it   x   int x    Since x has the number 1 in it  I can turn it in to a integer   To see if a string is a number  you can do this   def is number var       try          if var    int var               return True     except Exception          return False  x    1   y    test   x test   is number x   print x test    It should print to IDLE True because x is a number   y test   is number y   print y test    It should print to IDLE False because y in not a number

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T3     for i in range 0 len T1        T3 append         for j in range 0 len T1 i             b int T1 i  j           T3 i  append b   print T3

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If it s only a tuple of tuples  something like rows  map int  row  for row in rows  will do the trick   There s a list comprehension and a call to map f  lst   which is equal to  f a  for a in lst   in there    Eval is not what you want to do  in case there s something like   import    os   unlink  importantsystemfile   in your database for some reason  Always validate your input  if with nothing else  the exception int   will raise if you have bad input

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Instead of putting int     put float    which will let you use decimals along with integers

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I would agree with everyones answers so far but the problem is is that if you do not have all integers they will crash   If you wanted to exclude non-integers then  T1      13    17    18    21    32            07    11    13    14    28            01    05    06    08    15    16    new list   list list int a  for a in b  for b in T1 if a isdigit      This yields only actual digits   The reason I don t use direct list comprehensions is because list comprehension leaks their internal variables

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You can do something like this   T1      13    17    18    21    32             07    11    13    14    28             01    05    06    08    15    16      new list   list list int a  for a in b if a isdigit    for b in T1    print new list

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You can do this with a list comprehension   T2     int column  for column in row  for row in T1    The inner list comprehension   int column  for column in row   builds a list of ints from a sequence of int-able objects  like decimal strings  in row  The outer list comprehension       for row in T1    builds a list of the results of the inner list comprehension applied to each item in T1   The code snippet will fail if any of the rows contain objects that can t be converted by int  You ll need a smarter function if you want to process rows containing non-decimal strings   If you know the structure of the rows  you can replace the inner list comprehension with a call to a function of the row  Eg   T2    parse a row of T1 row  for row in T1

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I would rather prefer using only comprehension lists     int y  for y in x  for x in T1

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int   is the Python standard built-in function to convert a string into an integer value  You call it with a string containing a number as the argument  and it returns the number converted to an integer   gt  gt  gt  int  quot 1 quot     1 2  If you know the structure of your list  T1  that it simply contains lists  only one level   you could do this in Python 3  T2    list map int  x   for x in T1   In Python 2  T2    map int  x  for x in T1

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Yet another functional solution for Python 2   from functools import partial  map partial map  int   T1    Python 3 will be a little bit messy though   list map list  map partial map  int   T1      we can fix this with a wrapper  def oldmap f  iterable       return list map f  iterable    oldmap partial oldmap  int   T1

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Python has built in function int string  and optional parameter base  if your string contains an Integer value  it will convert that to the corresponding Integer value  However if you have decimnal number as string you ll need float   to convert it  Usage  a    22  b   int a   and if a    22 22  b   int a     will give error  invalid literal for int       b   float a     will convert the string

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I want to share an available option that doesn t seem to be mentioned here yet   rumpy random permutation x    Will generate a random permutation of array x  Not exactly what you asked for  but it is a potential solution to similar questions

[python] How to convert strings into integers in Python?

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