Наверняка вы замечали, что в Python есть удобная функция для получения переменной окружения
os.getenv(NAME)
И её "сестра" для создания или изменения переменных окружения
os.putenv(NAME, VALUE)
Но почему-то putenv() не работает как должно. Энвайромент не обновляется!
os.putenv('MYVAR', '1')
print(os.getenv('MYVAR'))
... и ничего 😴
Почему так?
На самом деле энвайромент обновляется, но это значение не добавляется в словарь os.environ.
Откройте исходник функции os.getenv(). Это просто шорткат для os.environ.get()
В то время как putenv() это built-in С-функция.
Словарь os.environ (или точней класс из MutableMapping) создаётся из энвайромента в момент инициализации. Функция putenv() самостоятельно его не изменяет.
В тоже время, когда вы создаёте или изменяете ключ в os.environ, автоматически вызывается putenv() в методе __setitem__().
То есть, технически putenv() всё делает верно, но в os.environ это не отражается. Можно проверить так:
>>> os.putenv('MYVAR', '123')
>>> os.system('python -c "import os;print(os.getenv(\'MYVAR\'))"')
123
Я объявил переменную в текущем процессе и вызвал дочерний процесс, который её унаследовал и получил в составе os.environ.
Аналогично при удалении переменной вызывается еще одна built-in функция unsetenv(), удаляющая переменную из системы.
Итого
▫️ Удобней всего явно обновлять переменные через os.environ
▫️ Есть способ неявно создать/удалить переменную через putenv/unsetenv, что не повлияет на os.environ но изменит энвайромент и передаст изменения сабпроцессам. Но так лучше не делать!
▫️os.environ это просто обертка для built-in функций putenv() и unsetenv().
#basic
🪐 The galaxy NGC 2683, sometimes called the "UFO Galaxy," has a dramatic, warped disk that gives it a shape unlike typical spirals. Located about 35 million light-years away in the constellation Lynx, its tilted, edge-on view and slightly twisted arms create the illusion of a flying saucer drifting through space, making it one of the most striking examples of galaxies with unusual forms. ✨
#galaxies⚡#shapes⚡#astronomy⚡#nasa⚡#galaxy⚡#stars⚡#universe⚡#cosmos⚡#space
👉subscribe Universe Mysteries
👉more Channels
🪐 The galaxy NGC 4710, located about 60 million light-years away in the constellation Coma Berenices, is famous for its strikingly thin, edge-on profile that makes it look more like a cosmic needle than a typical spiral or elliptical galaxy. This unusual "boxy/peanut-shaped" bulge is thought to form when a flat disk of stars buckles and warps over time, creating a rare structure that reveals the hidden dynamics shaping galactic evolution. ✨
#galaxies⚡#shapes⚡#astronomy⚡#nasa⚡#galaxy⚡#stars⚡#universe⚡#cosmos⚡#space
👉subscribe Universe Mysteries
👉more Channels
🪐 The galaxy UGC 2885, sometimes called "Rubin's Galaxy," sports an unusual appearance with its outsized, sprawling disk—nearly 2.5 times wider than the Milky Way. Its vast, faint spiral arms stretch for over half a million light-years, making it not only one of the largest known spiral galaxies but also a cosmic oddity that challenges ideas about how galaxies can grow and maintain such immense, delicate structures. ✨
#galaxies⚡#mysteries⚡#shapes⚡#nasa⚡#galaxy⚡#stars⚡#astronomy⚡#universe⚡#cosmos⚡#space
👉subscribe Universe Mysteries
🪐 The galaxy known as the Cartwheel Galaxy, located about 500 million light-years away in the constellation Sculptor, displays a striking ring-and-spoke structure unlike ordinary spirals or ovals. Its unusual shape was created when a smaller galaxy crashed through its center, sending waves of star formation racing outward and leaving behind bright, circular rings and faint, radial arms—an extraordinary cosmic ripple frozen in space. ✨
#galaxies⚡#shapes⚡#collisions⚡#nasa⚡#galaxy⚡#stars⚡#astronomy⚡#universe⚡#cosmos⚡#space
👉subscribe Universe Mysteries
👉more Channels
🪐 The galaxy NGC 1427A, found in the Fornax Cluster, looks nothing like a neat spiral or smooth oval—it's shaped like a cosmic boomerang. This odd appearance is the result of NGC 1427A plunging through the dense cluster, which causes its stars and gas to be pulled and stretched, creating a lopsided, arrowhead-like structure as it slowly gets torn apart by gravity. ✨
#galaxies⚡#shapes⚡#mystery⚡#nasa⚡#galaxy⚡#stars⚡#astronomy⚡#universe⚡#cosmos⚡#space
👉subscribe Universe Mysteries
🪐 Not all galaxies fit the classic spiral or oval shapes—take the galaxy LEDA 074886, located about 70 million light-years away, which stunned astronomers with its rare rectangular structure. Unlike the familiar swirls or smooth ellipses, LEDA 074886’s boxy outline is thought to be the result of a merger between two smaller galaxies, sculpting a cosmic shape almost never seen in the universe. ✨
#galaxies⚡#mergers⚡#shapes⚡#nasa⚡#galaxy⚡#stars⚡#astronomy⚡#universe⚡#cosmos⚡#space
👉subscribe Universe Mysteries
👉more Channels
🪐 The galaxy ESO 137-001, streaking through the Norma Cluster about 220 million light-years away, has a spectacular "tadpole" shape with long blue tails streaming out behind it. These tails are made of hot, stripped gas and young stars that formed as the galaxy plunges through the dense cluster, showing how powerful cosmic forces can stretch and reshape galaxies far beyond the classic spirals and ovals. ✨
#galaxies⚡#shapes⚡#cluster⚡#nasa⚡#galaxy⚡#stars⚡#astronomy⚡#universe⚡#cosmos⚡#space
👉subscribe Universe Mysteries
👉more Channels
🪐 The galaxy known as the Tadpole Galaxy (UGC 10214), about 420 million light-years away in the constellation Draco, is famous for its long, sweeping tail that stretches over 280,000 light-years. This striking "tadpole" shape was created when another galaxy passed close by, pulling out a stream of stars, gas, and dust—a cosmic encounter that gave the Tadpole Galaxy its unforgettable, bizarre silhouette among the galaxies. ✨
#galaxies⚡#shapes⚡#collision⚡#nasa⚡#galaxy⚡#stars⚡#astronomy⚡#universe⚡#cosmos⚡#space
👉subscribe Universe Mysteries
👉more Channels