How to modify a specific substring in a list of strings in Python?-CodePudding

Let's say I have a list like this:

rows = ['123', '456', '789']

and I try to modify the first character of the first string like this:

rows[0][0].replace('1','DDDD')

then when I print out the list, there is no change to it?

I know of a way to do it with list comprehension, but that iterates through the entire list which seems inefficient. Is there a way to just target one string in the list?

CodePudding user response：

.replace returns the mutated string, not changes it in place. You instead want to set your character to the returned value, like so:

rows[0]=rows[0].replace('1','DDDD')#changes all occurrences

If you only wanted to change the first character, you could do

rows[0]='DDDD' rows[0][1:]

But keep in mind that doesn't check the character.

CodePudding user response：

The function on it's own won't change the list value, you need to do this:

rows[0][0] = rows[0][0].replace('1','DDDD')

CodePudding user response：

rows = ['123', '456', '789']

1.using list comprehension, map function and lambda 2.Replace substring in list of strings

result = list(map(lambda st: str.replace(st, "3", "0"), rows)) result -> ['120', '456', '789']