iteration
range()
Returns an immutable range object representing an arithmetic sequence of integers. Memory-efficient — values are computed lazily, not stored.
range(stop) | range(start, stop[, step])Parameters
| Parameter | Purpose |
|---|---|
| start | First value (default 0) |
| stop | Exclusive upper bound (required) |
| step | Increment between values (default 1, cannot be 0) |
Examples
list(range(5))Returns [0, 1, 2, 3, 4]
list(range(2, 10, 2))Returns [2, 4, 6, 8]
list(range(10, 0, -1))Returns [10, 9, ..., 1]
Gotcha
range() returns a range object, NOT a list — printing it shows 'range(0, 5)'. Wrap in list() to see values.
Related built-ins
enumerate()
Yields (index, item) tuples from an iterable. Preferred over manual index counters in for-loops.
map()
Applies a function to each item of one or more iterables, yielding results lazily. Returns a map object (iterator), not a list.
filter()
Yields items from iterable for which function(item) is truthy. If function is None, filters out falsy items.
zip()
Pairs elements from multiple iterables into tuples, stopping at the shortest. With strict=True, raises ValueError if lengths differ.