Using replace() method in python by index [duplicate]

Question

I want to do something like this.

example_string = "test"
print(example_string.replace(example_string[0], "b"))

expecting the output

best

however because the letter "t" is being passed into the method the t at the end also gets replaced with a "b". Resulting in the output

besb

How do I do it in a way that would result in the output "best" instead of "besb"?

Answer 1

The problem is that .replace(old, new) returns a copy of the string in which the occurrences of old have been replaced with new.

Instead, you can swap the character at index i using:

new_str = old_str[:i] + "b" + old_str[i+1:]

Answer 2

Check the documentation.

You can use

example_string.replace(example_string[0], "b", 1)

though it would be much more natural to use a slice to replace just the first character, as @nbryans indicated in a comment.