Converting all elements to strings in a list of list in Python

Question

I have a list of list which has both integers and strings inside it as their values. Now I want to convert all the values to string.

My list of list looks like : (say final_rule)

[[3, '*', 1, 4, 1], [1, 2, '*', 2, 1], ['*', '*', 3, 4, 1], [2, 2, '*', 2, 1]]

And I am trying to produce an output as:

[['3', '*', '1', '4', '1'], ['1', '2', '*', '2', '1'], ['*', '*', '3', '4', '1'], ['2', '2', '*', '2', '1']]

I am trying the below code:

new_list=[]
for list_ in final_rule:
    #print("list_:",list_)
    [str(i) for i in list_]
    new_list.append(i)
return new_list

STerliakov · Accepted Answer · 2022-05-13 10:03:29Z

2

You are close! Comprehension is fine, but it does not modify list in place, it creates a new one. So you need to append new list:

def stringify(final_rule):
    new_list=[]
    for list_ in final_rule:
        #print("list_:",list_)
        strings = [str(i) for i in list_]
        new_list.append(strings)
    return new_list

But you can achieve the same with a single comprehension:

def stringify(final_value):
    return [[str(i) for i in inner] for inner in final_value]

Alternatively, inner list may be constructed with list(map(str, inner)), but I'm not sure what will be faster.

answered May 13, 2022 at 10:03

STerliakov

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shivankgtm · Accepted Answer · 2022-05-13 11:42:18Z

2

int_list = [[3, '*', 1, 4, 1], [1, 2, '*', 2, 1], ['*', '*', 3, 4, 1], [2, 2, '*', 2, 1]]

# you can use nested loop like following.
str_list = [[str(i) for i in j] for j in int_list]

output

[['3', '*', '1', '4', '1'],
 ['1', '2', '*', '2', '1'],
 ['*', '*', '3', '4', '1'],
 ['2', '2', '*', '2', '1']]

edited May 13, 2022 at 11:42

answered May 13, 2022 at 9:59

shivankgtm

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4 Comments

Dev Over a year ago

Can you explain a little?

shivankgtm Over a year ago

Dev that is just another way of writing nested loops in a single line.

Dev Over a year ago

What is data in the code?

shivankgtm Over a year ago

@Dev edited, that was int_list. my bad.

cards · Accepted Answer · 2022-05-13 10:05:19Z

1

lst = [[3, '*', 1, 4, 1], [1, 2, '*', 2, 1], ['*', '*', 3, 4, 1], [2, 2, '*', 2, 1]]

list(list(map(str, terms)) for terms in lst)

answered May 13, 2022 at 10:05

cards

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Comments

Surya Narayan Jena · Accepted Answer · 2022-05-13 10:05:51Z

1

Here is one way of doing it using the map() and List Comprehension.

a = [[3, '*', 1, 4, 1], [1, 2, '*', 2, 1], ['*', '*', 3, 4, 1], [2, 2, '*', 2, 1]]
result = [list(map(str,x)) for x in a]

answered May 13, 2022 at 10:05

Surya Narayan Jena

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