Replace commas with dots in a string column pandas without nan values

Question

I have a dataset with a string column. I'm searching to replace comma with dot, but when i use str.replace method, for some rows (maybe for integer values), it return NaN values.

df['code_input'] = df['code_input'].str.replace(',', '.')

How can i do it?

Example of my desidered dataset:

code_input	desidered_code_output
15.5C72HT	15.5C72HT
46,3C8,4HTT	46.3C8.4HTT
40	40
...	...

Example of my desidered with str.replace method:

code_input	desidered_code_output
15.5C72HT	15.5C72HT
46,3C8,4HTT	46.3C8.4HTT
40	NaN
...	...