Use Python built-in replace() function to replace the first character in the string. The str.replace takes 3 parameters old, new, and count (optional).
Where count indicates the number of times you want to replace the old substring with the new substring.
str.replace(old, new[, count])
Example replace the first character in a string Python
Simple example code using replace() function to returns a copy of the string with all occurrences of substring old replaced by new.
s = "Hello World!"
res = s.replace("H", "X", 1)
print(res)
Output:

If you don’t want to use str.replace()
, you can manually do it by taking advantage of splicing
s = "Hello World!"
def rep(s, char, index):
return s[:index] + char + s[index + 1:]
# Test
res = rep(s, "Z", 0)
print(res)
Output: Zello World!
Another way
How to change character in string Python. Use the list() and join the funciton.
s = "Hello World!"
new = list(s)
new[0] = 'Y'
print(''.join(new))
Output: Yello World!
Do comment if you have any doubts and suggestions on this Python string topic.
Note: IDE: PyCharm 2021.3.3 (Community Edition)
Windows 10
Python 3.10.1
All Python Examples are in Python 3, so Maybe its different from python 2 or upgraded versions.

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