Python Morsels: Boolean operators

2 weeks ago 12

Club.noww.in

Python's Boolean operators are used for combining Boolean expressions and negating Boolean expressions.

Table of contents

Combining two if statements using and

Here we have a program called word_count.py:

words_written_today = int(input("How many words did you write today? "))

if words_written_today < 50_000/30:
    print("Yay! But you need to write more still.")
else:
    print("Congratulations!")

This program has an if statement that checks whether we've written enough words each day, with the assumption that we need to write 50,000 words every 30 days.

If our word count is under 1,666 words (50,000 / 30) it will say we need to write more:

$ python3 word_count.py
How many words did you write today? 500
Yay! But you need to write more still.

We'd like to modify our if condition to also make sure that we only require this if today's date is in the month of November.

We could do that using Python's datetime module:

>>> from datetime import date
>>> is_november = date.today().month == 11

That is_november variable will be True if it's November and False otherwise:

>>> is_november
False

If we combine this with the code we had before, we could use two if statements:

from datetime import date

words_written_today = int(input("How many words did you write today? "))
is_november = date.today().month == 11

if words_written_today < 50_000/30:
    if is_november:
        print("Yay! But you need to write more still.")
    else:
        print("Congratulations!")
else:
    print("Congratulations!")

One of our if statements checks whether we're under our word limit. The other if statement checks whether it's the month of November. If both are true then we end up printing out that we still need to write more words. Otherwise we print a success message:

$ python3 word_count.py
How many words did you write today? 500
Congratulations!

This works, but there is a better way to write this code.

We could instead use Python's and operator to combine these two conditions into one:

from datetime import date

words_written_today = int(input("How many words did you write today? "))
is_november = date.today().month == 11

if is_november and words_written_today < 50_000/30:
    print("Yay! But you need to write more still.")
else:
    print("Congratulations!")