Ravindra BagaleCourses & study guides मराठी Track your progress

Python Variables and Data Types Explained for Beginners (int, float, str, bool)

P2.5 What Is None in Python

By , trainer LinkedIn Last updated:

Why. Real data has missing values: a phone number not given, a delivery not yet done. Python uses None for "no value yet".

What. None is a special value that means nothing is there. It is not 0 and not an empty text. In pandas, missing values show as NaN or None.

How.

Check for a missing value

  1. Store None when a value is unknown.
  2. Test it with is None.
  3. Decide what to do: skip it or fill a default.

Worked example A — A missing delivery time.

Step 1 — What we do. A courier in Lagos has not delivered yet, so the delivery time is unknown.

Step 2 — Type and run this code.

delivered_at = None
print(delivered_at)
print(delivered_at is None)

Step 3 — Output you should see.

None
True

Step 4 — What it means. is None gives True, so we know the value is missing. Use is None, not == None.

Worked example B — Fill a default when missing.

Step 1 — What we do. If the customer city is missing, we use "Unknown".

Step 2 — Type and run this code.

city = None
if city is None:
    city = "Unknown"
print(city)

Step 3 — Output you should see.

Unknown

Step 4 — What it means. This is the same idea as fillna in pandas, just for one value. (We learn if properly in the if/else chapter.)

Ravindra Bagale's Tip

0 means "zero", None means "we do not know". Never put 0 for a missing amount — it will pull your average down.

Samajla ka? If yes, take the quiz for this chapter. If not, run every example again and change one value each time.