all Python 3osfunction

os.getenv

os — environment

Return an environment variable's value, or default if unset.

Syntax

os.getenv(key, default=None)

The value is always a string, and the default comes back as is, unconverted: write int(os.getenv('PORT', '8000')) for a number rather than int(os.getenv('PORT', 8000)), which mixes types. An empty variable and a missing one differ: a variable set to an empty string returns '', not the default. It reads from os.environ, a snapshot taken when Python started.

Examples

import os
os.environ['APP_MODE'] = 'debug'
print(os.getenv('APP_MODE'))   # → debug
print(os.getenv('NO_SUCH_VAR_XYZ', 'default'))   # → default
print(os.getenv('NO_SUCH_VAR_XYZ'))   # → None
print(int(os.getenv('RETRIES', '3')) + 1)   # → 4 — из окружения приходят только строки, число нужно привести явно
print(os.getenv('APP_MODE') == os.environ.get('APP_MODE'))   # → True — getenv это сокращение для os.environ.get

See also

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