There are a number of problems:

• The syntax of your path.replace line is incorrect. \ is an escape character and as such it needs to be escaped by prepending another \.
• path.replace works the other way around: first the thing you want to substitute, then the thing you want to substitute it with.
• Your string doesn't contain all of the backslashes anymore, because they have been interpreted as ... escape characters. You need to create a "raw" string.

Putting it all together:

path = r"/Users/xx/datasets/yyy/DefinedTS\Training\00000"
path.replace("\\", "/")
print(path)

There are a number of problems:

• The syntax of your path.replace line is incorrect. \ is an escape character and as such it needs to be escaped by prepending another \.
• path.replace works the other way around: first the thing you want to substitute, then the thing you want to substitute it with.
• Your string doesn't contain all of the backslashes anymore, because they have been interpreted as ... escape characters. You need to create a "raw" string.

Putting it all together:

path = r"/Users/xx/datasets/yyy/DefinedTS\Training\00000"
path = path.replace("\\", "/")
print(path)