In Python how do I convert all of the items in a list to floats

Question

I have a script which reads a text file  pulls decimal numbers out of it as strings and places them into a list   So I have this list     0 49    0 54    0 54    0 54    0 54    0 54    0 55    0 54    0 54     0 54      0 55    0 55    0 55    0 54    0 55    0 55    0 54    0 55    0 55    0 54     How do I convert each of the values in the list from a string to a float   I have tried   for item in list      float item    But this doesn t seem to work for me

User · Answer

map float  mylist  should do it     In Python 3  map ceases to return a list object  so if you want a new list and not just something to iterate over  you either need list map float  mylist  - or use SilentGhost s answer which arguably is more pythonic

User · Answer

I had to extract numbers first from a list of float strings      df4  sscore     df4  simscore   str findall   d    d      then each convert to a float      ad       for z in range len df4          ad append  float i  for i in df4  sscore   z      in the end assign all floats to a dataframe as float64      df4  fscore     np array ad dtype float

User · Answer

This is how I would do it   my list     0 49    0 54    0 54    0 54    0 54    0 54    0 55    0 54         0 54    0 54    0 55    0 55    0 55    0 54    0 55    0 55    0 54         0 55    0 55    0 54   print type my list 0     prints  lt type  str  gt  my list    float i  for i in my list  print type my list 0     prints  lt type  float  gt

User · Answer

for i in range len list    list i  float list i

User · Answer

float i  for i in lst    to be precise  it creates a new list with float values  Unlike the map approach it will work in py3k

User · Answer

you can use numpy to avoid looping  import numpy as np list np array my list  astype float

User · Answer

you can even do this by numpy  import numpy as np np array your list dtype float    this return np array of your list as float  you also can set  dtype  as int

User · Answer

This would be an other method  without using any loop    import numpy as np list np float  list name

User · Answer

import numpy as np my list     0 49    0 54    0 54    0 54    0 54    0 54    0 55    0 54    0 54    0 54    0 55    0 55    0 55    0 54    0 55    0 55    0 54     0 55    0 55    0 54   print type my list   type my list 0          lt class  list  gt   lt class  str  gt    which displays the type as a list of strings  You can convert this list to an array of floats simultaneously using numpy       my list   np array my list  astype np float       print type my list   type my list 0             lt class  numpy ndarray  gt   lt class  numpy float64  gt

User · Answer

I have solve this problem in my program using   number input   float     1f   format float input      list append number input

User · Answer

float item  do the right thing  it converts its argument to float and and return it  but it doesn t change argument in-place  A simple fix for your code is   new list      for item in list      new list append float item     The same code can written shorter using list comprehension  new list    float i  for i in list   To change list in-place   for index  item in enumerate list       list index    float item    BTW  avoid using list for your variables  since it masquerades built-in function with the same name

User · Answer

You can use numpy to convert a list directly to a floating array or matrix       import numpy as np     list ex    1  0    This a list     list int   np array list ex    This is a numpy integer array   If you want to convert the integer array to a floating array then add 0  to it      list float   np array list ex    0    This is a numpy floating array

[python] In Python, how do I convert all of the items in a list to floats?

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