A return value is the object a function supplies to its caller when it completes. It forms part of an API’s output contract alongside system actions and exceptions. Applications commonly orchestrate function calls by feeding returned values into later functions. section 3.1.3
Useful properties of return values include:
- Because Python functions return objects, they can return tuples or other compound values rather than only scalar results. section 3.1.3
- A function without an explicit return statement returns None automatically; functions performing system actions can return True or False to report success or failure. section 3.2.3
- Returning data instead of printing it keeps a function reusable and makes its behavior easier to test. section 3.2.4
Returning and unpacking multiple values
abs(-10) returns 10. A split_fullname function can return a three-item tuple, allowing callers to write fname, mname, lname = split_fullname("John James Smith"). The caller may also retain the result as one tuple. section 3.1.3
def full_name(fnameNone, mname=None, lname=None) -> str:
"""Concatenates the names together and returns the full name
Arguments:
fname {str} -- first name
mname {str} -- middle name
lname {str} -- last name
Returns:
str -- the full name with only a single space between names
"""
full_name = " ".join(name for name in [fname, mname, lname] if name)
return full_name
Prefer a focused function that returns the constructed full name; callers can print it, place it in a web page or data structure, convert it to JSON, and test it directly. section 3.2.4
