What is a lambda function and when to use it?

Question

Accepted Answer

**Lambda** is an anonymous (unnamed) function defined in one line.

**Syntax:**
```python
lambda arguments: expression
```

**Examples:**
```python
# Simple lambda
square = lambda x: x ** 2
print(square(5))  # 25

# Multiple arguments
add = lambda a, b: a + b
print(add(2, 3))  # 5

# With condition
max_value = lambda a, b: a if a > b else b
```

**When to use:**
- Short functions for `sorted()`, `filter()`, `map()`.
- Callbacks.

```python
# sorted with lambda
points = [(1, 2), (3, 1), (5, 4)]
sorted_points = sorted(points, key=lambda p: p[1])

# filter
evens = list(filter(lambda x: x % 2 == 0, range(10)))

# map
doubles = list(map(lambda x: x * 2, range(5)))
```

**Don't use for complex logic** — use def.

Python: What is a lambda function and when to use it?