Python ยท Chapter 22 of 45
Python Lambda
A `lambda` is a small anonymous function limited to a single expression. Handy for short throwaway functions.
Syntax: `lambda parameters: expression`.
When to use
Use lambda for tiny functions passed as arguments to `sorted`, `map`, `filter`, etc. Define with `def` for anything longer.
Limitations
No statements (like `if/else` blocks or assignments) โ only a single expression that becomes the return value.
Example 1 (python)
square = lambda x: x * x
print(square(5))Output
25One-liner function assigned to a variable.
Example 2 (python)
pairs = [(1,"b"),(2,"a"),(3,"c")]
sorted_pairs = sorted(pairs, key=lambda p: p[1])
print(sorted_pairs)Output
[(2, 'a'), (1, 'b'), (3, 'c')]Sort by second element using a lambda key.
Key points
- Anonymous single-expression function.
- Syntax: `lambda args: expression`.
- Great as a `key=` for sort/map/filter.
- Prefer `def` for anything multi-line.
๐ก Note: Assigning a lambda to a name (`f = lambda x: ...`) is discouraged by PEP 8 โ use `def f(x):` instead.