Python · Functions: Parameters & Scope

Mutating an argument inside a function sometimes changes the caller's object and sometimes doesn't. What determines which?

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More in Functions: Parameters & Scope

What does this print? ``` def f(x, acc=[]): acc.append(x) return acc print(f(1)) print(f(2)) ```

When is a parameter's default value expression actually evaluated?

What does this print? ``` def f(a=[1, 2, 3]): a += [4, 5] print(a) f() f() ```

In a function definition, where must parameters with default values be placed, and why?

A function ends without ever executing a return statement. What does calling it evaluate to?

What does this print, and why? ``` def my_sum(a, b, c=0, d=0): return a + b + c + d print(my_sum(d=1, b=3, c=2, a=1)) ```

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