all Python 3osfunction

os.putenv

os — environment

Set an environment variable at the OS level (for child processes).

Syntax

os.putenv(key, value)

It does not update os.environ: after putenv('X', '1') the expression 'X' in os.environ is false. So os.environ['X'] = '1' is almost always better — it calls putenv itself and keeps things consistent. Child processes started after the call see the change. On macOS and FreeBSD repeatedly setting variables may leak memory.

Examples

import os
os.putenv('GLOSSARY_DEMO', '42')   # → значение ушло в окружение ОС: его унаследуют дочерние процессы
print(os.environ.get('GLOSSARY_DEMO'))   # → None (putenv не обновляет словарь os.environ)
os.environ['GLOSSARY_DEMO'] = '42'   # → штатный способ: присваивание в os.environ само вызывает putenv
print(os.getenv('GLOSSARY_DEMO'))   # → 42
os.putenv('GLOSSARY_DEMO', 42)   # → TypeError: значение обязано быть str или bytes, а не int

See also

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