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array.array

arrays

A compact mutable array of numbers of one type, set by a type code ('i', 'd', 'B'…); it stores raw values, not objects.

Syntax

array.array(typecode[, initializer])

A list stores pointers to separate int objects (8 bytes per reference plus the object itself), while an array stores bare numbers of itemsize bytes each, so a million ints in 'i' take about 4 MB instead of 30+. The price is strictness: 'i' rejects 1.5 (TypeError) and 'b' rejects 200 (OverflowError). There is no vector maths: a * 2 repeats the array as a list would rather than multiplying the numbers — that is what numpy is for.

Examples

import array, sys
nums = array.array('i', range(1000))
print(nums.itemsize * len(nums))  # → 4000
print(sys.getsizeof(nums) < sys.getsizeof(list(range(1000))))  # → True
print(nums[:3] * 2)  # → array('i', [0, 1, 2, 0, 1, 2]) — повтор, а не умножение

import array
a = array.array('b', [1, 2])
try:
    a.append(1.5)
except TypeError:
    print('дробное не влезет')  # → дробное не влезет
try:
    a.append(200)
except OverflowError as e:
    print(e)  # → signed char is greater than maximum
print(array.array('B', b'abc').tolist())  # → [97, 98, 99]

See also

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