Summary: Selection using if

We have seen three ways of using the if statement to_select_statements to execute.

One possibility is that we have a statement (simple or compound) to execute conditionally. The construct to use is:

if test-expression:
    true-statement

A second possibility is that we want to select one of two statements to execute. In this case the construct is:

if test-expression:
    true-statement
else:
    false-statement

The third possibility is that we want to select one of a number of mutually exclusive statements to execute. In this case the construct is:

if test-expression:
    true-statement
elif test-expression:
    true-statement
...
else:
    false-statement

with as many elif statements as required to cover all the possibilities, and the else statement usually reserved for catching errors (specifically invalid values).