2. Functions def

• We learned some Python functions: len, int, float, print, and input.

• Now we will create our own functions.

• I use def to define the function and return to return a value.

• There are functions that do not return anything.

1 def is_even(x): 2     return x % 2 == 0 3 4 5 print(is_even(13)) 6 print(is_even(12)) Edit this code line that just executed next line to execute << First < Prev Next > Last >> Step 1 of 9 Submit Python Tutor by Philip Guo Customize visualization (NEW!)

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• This function returns True if the parameter x is even, False otherwise.

• Note that, unlike what we have seen so far, these lines of code will not be executed immediately.

• It is necessary to call the function to execute them.

2.1. Example

• Define a function factorial

1 def factorial(n): 2     f = 1 3     while n > 0: 4         f = f * n 5         n = n - 1 6     return f 7 8 9 for i in range(5): 10     print(factorial(i)) Edit this code line that just executed next line to execute << First < Prev Next > Last >> Step 1 of 67 Submit Python Tutor by Philip Guo Customize visualization (NEW!)

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Activity: CodeLens 2.1.1 (cl_l20_2b_en)

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