Python Functions Tutorial: def, return, Arguments and lambda with Examples

P7.5 Python lambda Functions Explained with Examples

By Ravindra Bagale, trainer LinkedIn Last updated: 27 October 2026

Why. Sometimes you need a tiny function only once — for sorting or for pandas apply. lambda writes it in one line.

What. lambda x: expression is a small function without a name. It can only hold one expression.

How.

Use a lambda

Write lambda, the input name, a colon.
Write the expression to return.
Pass it where a function is expected (like key= in sorted).

Worked example A — A lambda stored in a variable.

Step 1 — What we do. Convert euros to dollars at 1.08.

Step 2 — Type and run this code.

to_usd = lambda eur: round(eur * 1.08, 2)
print(to_usd(250))

Step 3 — Output you should see.

270.0

Step 4 — What it means. Same as a def with return, just shorter.

Worked example B — Sort records by a field.

Step 1 — What we do. Sort employees of an IT firm by salary.

Step 2 — Type and run this code.

staff = [
    {"name": "Kenji", "salary": 72000},
    {"name": "Olivia", "salary": 88000},
    {"name": "Ravi", "salary": 65000},
]
for s in sorted(staff, key=lambda r: r["salary"], reverse=True):
    print(s["name"], s["salary"])

Step 3 — Output you should see.

Olivia 88000
Kenji 72000
Ravi 65000

Step 4 — What it means. key=lambda r: r["salary"] tells sorted what to compare. pandas: df.sort_values("salary").

Python next to other languages — a tiny function. You do not need to learn these other languages. This only shows why Python is easier to read.

Language	Code
Python	`lambda x: x * 2`
Java	`x -> x * 2`
JavaScript	`x => x * 2`
Go	`func(x int) int { return x * 2 }`

Ravindra Bagale's Tip

If a lambda does not fit comfortably in one line, use def. Named functions are easier to test.