Time for action – deciding with the if statement

We can use the if statement in the following ways:

  1. Check whether a number is negative as follows:
    >>> if 42 < 0:
...     print('Negative')
... else:
...     print('Not negative')
...
Not negative

    In the preceding example, Python decided that 42 is not negative. The else clause is optional. The comparison operators are equivalent to the ones in C++, Java, and similar languages.

  2. Python also has a chained branching logic compound statement for multiple tests similar to the switch statement in C++, Java, and other programming languages. Decide whether a number is negative, 0, or positive as follows:
    >>> a = -42
>>> if a < 0:
...     print('Negative')
... elif a == 0:
...     print('Zero')
... else:
...     print('Positive')
...
Negative

    This time, Python decided that 42 is negative.

What just happened?

We learned how to do branching logic in Python.

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