all Python 3structfunction

struct.calcsize()

format

Returns the number of bytes a struct format occupies when packed.

Syntax

struct.calcsize(format)

The result depends on the prefix: without one (or with '@') sizes are native and padding is inserted between fields, so calcsize('ci') is 8 on a typical 64-bit machine while calcsize('<ci') is 5. No padding is added at the end: 'ic' and 'ci' give different sizes. For files and networks use '<', '>' or '!' — sizes are standard there and the same everywhere.

Examples

import struct
print(struct.calcsize('<ci'))  # → 5
print(struct.calcsize('ci'))  # → ? 8 на типичной 64-битной машине — выравнивание
print(struct.calcsize('!HHI'))  # → 8

See also

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