Make changes to a list of strings within a for loop

Question

I have a list that looks like this ["first letter", " second letter", " third letter"]In some cases, the first character is an empty character " ". In these cases, I want to strip off the first character and modify my list to become like this:

["first letter", "second letter", "third letter"]

How can I achieve this? This doesnt work because I am not modifying the string itself and there can be more than 1 " " characters in each string. I only want to remove the first.

    for i in setOfCoordinates:
        if i[0] == ' ':
            print('space found')
            i.replace(" ", "")

I don't want to remove all spaces, just the first one

for i in setOfCoordinates:. You are already iterating over the elements of the list. Fetching i[0] will fetch the first character of the element. Replace i[0] with i — user15801675
– user15801675, Commented Aug 6, 2021 at 8:56
test = [i.lstrip() for i in setOfCoordinates] removes all spaces also. :) — Cow
– Cow, Commented Aug 6, 2021 at 8:57
That is intentional. I want to fetch the first character and check if its an empty character. If its empty, then I want to strip it off @Sujay — x89
– x89, Commented Aug 6, 2021 at 8:58
I don't want to remove all spaces, just the first one @user56700 — x89
– x89, Commented Aug 6, 2021 at 8:59

Hailey · Accepted Answer · 2021-08-06 09:11:01Z

2

my =  ["first letter", " second letter", " third letter"]
for i in range(0,len(my),1):
    if my[i][0] == " " :
        my[i] = my[i][1:]
print(my)

# result : ['first letter', 'second letter', 'third letter']

I used the 'for' function. After that, through 'Slice', the string was truncated if the front was blank.

answered Aug 6, 2021 at 9:11

Hailey

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user15801675 · Accepted Answer · 2021-08-06 09:03:37Z

1

Try this. Use enumerate. Also, replace is not an in place function. It will return the replaced string. So, you can use string concatenation. i[0]+i[1:] which concatenate the string.

l=["first letter", " second letter", " third letter"]
for j,i in enumerate(l):
    if i[0]==" ":
        print("Space found")
        l[j]=i[0].replace(" ",'')+i[1:]
        print("Space removed")
print(l)

Output:

Space found
Space removed
Space found
Space removed
['first letter', 'second letter', 'third letter']

answered Aug 6, 2021 at 9:03

user15801675

Comments

SevC_10 · Accepted Answer · 2021-08-06 09:11:55Z

0

Just use the count parameter of the replace function: https://docs.python.org/3/library/stdtypes.html#str.replace

In your case:

i.replace(" ", "", 1)

just replaces 1 occurrence of " "

In order to modify the strings in the list, use their index (credit to @Sujay answer):

l = ["first letter", " second letter", " third letter"]
for j, i in enumerate(l):
    if i[0] == " ":
        print("Space found")
        l[j] = l[j].replace(" ", "",1)
print(l)

edited Aug 6, 2021 at 9:11

answered Aug 6, 2021 at 9:04

SevC_10

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2 Comments

x89 Over a year ago

but if the first char isn't a space, it would remove the middle space, no?

SevC_10 Over a year ago

In that case yes, but first you check if the first character is a space, then apply the replace

Sefan · Accepted Answer · 2021-08-06 09:26:36Z

0

You are looking for str.lremoveprefix() if you want to remove the first space but not the spaces after the letters. See more info on https://docs.python.org/3/library/stdtypes.html

setOfCoordinates = [" first letter", "  second letter  ", "   third letter   "]
print(setOfCoordinates) #[' first letter', '  second letter  ', '   third letter   ']
setOfCoordinates = [i.removeprefix(" ") for i in setOfCoordinates]
print(setOfCoordinates) #['first letter', ' second letter  ', '  third letter   ']

edited Aug 6, 2021 at 9:26

answered Aug 6, 2021 at 9:00

Sefan

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4 Comments

x89 Over a year ago

but doesn't modify the original list

Sefan Over a year ago

@x89 code is now updated and now modify the original list

SevC_10 Over a year ago

lstrip strips all leading spaces, not just one

Sefan Over a year ago

@SevC_10, my bad, its str.removeprefix() we are looking for here. Updating the answer

Debjyoti Banerjee · Accepted Answer · 2021-08-06 09:16:45Z

-1

x = ["first letter", " second letter", " third letter"]
x = [i.strip() for i in x] #### remove space from both the ends
print(x)

removing space from the start

x = ["first letter", " second letter", " third letter"]
x = [i.lstrip() for i in x]
print(x)

removing space from end

x = ["first letter", " second letter", " third letter"]
x = [i.rstrip() for i in x] #### remove space from both the ends
print(x)

answered Aug 6, 2021 at 9:16

Debjyoti Banerjee

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2 Comments

SevC_10 Over a year ago

strip functions remove all trailing or leading spaces, not just one

Debjyoti Banerjee Over a year ago

That's why I have shown for all. Whichever he wants to use can use it.

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