Python: Why Does str.split() Return a list While str.partition() Returns a tuple?

Question

Comparing Python's str.split() with str.partition(), I see that they not only have different functions (split() tokenizes the whole string at each occurrence of the delimiter, while partition() just returns everything before and everything after the first delimiter occurrence), but that they also have different return types. That is, str.split() returns a list while str.partition() returns a tuple. This is significant since a list is mutable while a tuple is not. Is there any deliberate reason behind this choice in the API design, or is it "just the way things are." I am curious.

Answer 1

The key difference between those methods is that split() returns a variable number of results, and partition() returns a fixed number. Tuples are usually not used for APIs which return a variable number of items.

Answer 2

@yole answer summarise the reasoning why partition() returns tuple. But there is a nice way to "exploit" that fact. I found below example in "Automate the boring stuff with Python".

   before, sep, after = 'Hello, world!'.partition(' ')
   print(before)