Python: change format for all elements in a list of strings

Question

I have a list of strings:

a = ['[1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0]',
     '[2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0]',
     '[3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0]',
     '[4.0, 4.0, 4.0, 4.0, 4.0, 4.0, 4.0]',
     '[5.0, 5.0, 5.0]', 
     '[1.0]'
    ]

When I use the code as below, the format for every element in the list is string, not the int.

a= tuple(a.reshape(1,-1)[0])

What I need to do is change the format for all elements. Such as

a[1][2] = 2

However, in my code:

a[1][2] = '.'

a is a list of strings.

timgeb
– timgeb

2014-06-19 19:56:30 +00:00
Commented Jun 19, 2014 at 19:56 — timgeb
– timgeb, Commented Jun 19, 2014 at 19:56

timgeb · Accepted Answer · 2014-06-20 12:08:17Z

4

a is a list of strings. I don't know where you got it from, but as far as I understand your question you want it to be a list of lists which contain numbers. This might be a use case for the eval function.

>>> a
['[1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0]', '[2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0]', '[3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0]', '[4.0, 4.0, 4.0, 4.0, 4.0, 4.0, 4.0]', '[5.0, 5.0, 5.0]', '[1.0]']
>>> a = [eval(x) for x in a]
>>> a
[[1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0], [2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0], [3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0], [4.0, 4.0, 4.0, 4.0, 4.0, 4.0, 4.0], [5.0, 5.0, 5.0], [1.0]]
>>> a[1][2]
2.0

If you do not want to use eval, I would suggest

a = [[float(x) for x in liststring[1:-1].split(',')] for liststring in a]

edited Jun 20, 2014 at 12:08

answered Jun 19, 2014 at 20:00

timgeb

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1 Comment

Ben Over a year ago

haha, almost at the exact same time. Yeah, I feel the same, eval makes me feel uneasy, but I don't think this is going to be used to execute code dynamically

Ben · Accepted Answer · 2014-06-19 20:00:56Z

1

How about this:

>>> a =['[1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0]', '[2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0]','[3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0]','[4.0, 4.0, 4.0, 4.0, 4.0, 4.0, 4.0]','[5.0, 5.0, 5.0]','[1.0]']
>>> a
['[1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0]', '[2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0]', '[3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0]', '[4.0, 4.0, 4.0, 4.0, 4.0, 4.0, 4.0]', '[5.0, 5.0, 5.0]', '[1.0]']
>>> a2 = [eval(l) for l in a]
>>> a2[1][2]
2.0

answered Jun 19, 2014 at 20:00

Ben

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Comments

pzp · Accepted Answer · 2014-06-20 12:40:43Z

Just use the JSON module; it is made specifically for these kinds of jobs. I made an example below. It converts all the items of list a (which are strings originally) into lists of floats. If you want to convert them to ints, just iterate through the nested lists and make blahblah = int(blahblah) (just be careful that you don't put something into the list that can't be converted into an integer, such as "s").

from json import loads

a = ['[1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0]',
 '[2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0]',
 '[3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0]',
 '[4.0, 4.0, 4.0, 4.0, 4.0, 4.0, 4.0]',
 '[5.0, 5.0, 5.0]', 
 '[1.0]'
]

for nestlist in range(len(a)):
    a[nestlist] = loads(a[nestlist])

print a

Hope this helps!
Palmer :)

Josh KG · Accepted Answer · 2014-07-17 16:49:49Z

1

Your a is a list of strings, not a list of lists. It should be:

a = [[1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0],
[2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0],
[3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0, 3.0],
[4.0, 4.0, 4.0, 4.0, 4.0, 4.0, 4.0],
[5.0, 5.0, 5.0],
[1.0]]

EDIT -- AN ACTUAL ANSWER:

Okay I realize this is an old problem for you now, but I just ran across another solution that does not use eval() (and thus avoids the security issues). Your list of strings a can be decoded using the json module and then turned into a new list of lists:

import json

def decodeList(list_of_strings):
    newList = list()
    for i in list_of_strings:
         newList.append(json.loads(i))
    return newList

a = decodeList(a)

print a[1][2]

# outputs 2.0

EDIT AGAIN:

Haha I just read through the rest of the answers and noticed someone already offered this one! Sigh. Nevermind.

edited Jul 17, 2014 at 16:49

answered Jun 19, 2014 at 20:01

Josh KG

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2 Comments

Jeremy_Tamu Over a year ago

Bro, I know what you mean. However, my case is a list of list. I want to find any element as an int. in my list, not a string

Josh KG Over a year ago

Ah, sorry misunderstood the issue. @timgeb looks like a working answer then!

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