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
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Crypto Snapshot [23 Dec] 📰
Highlights:
🔸Whales accumulate $726 Million In #Bitcoin
🔸Bank of International Settlements allow banks to hold 2% in #cryptocurrencies
🔸High net-worth investors continue to seek access to #crypto
Full read here.
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▫️ the risk of high inflation / currency instability;
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💰Cryptocurrencies: Last Week Tonight with John Oliver
Another take on #Bitcoin, other #CryptoCurrencies & #Blockchain. A must-watch.
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🔗 What is #Blockchain?
A technology that underpins #cryptocurrencies like #Bitcoin and presents new opportunities for how we share data.
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🌀 http://prs.pctvix.co/TelegramIX
Haveno
https://github.com/haveno-dex/haveno
Private and decentralized way to #exchange#Monero for national currencies or other #cryptocurrencies. Haveno uses peer-to-peer networking and multi-signature escrow to facilitate trading without a trusted third party custodian. Disputes can be resolved using non-custodial arbitration. Everything is built around Monero and Tor.
Haveno is the Esperanto word for "Harbor". The project is stewarded by a core Team, currently formed by 2 people: ErCiccione and Woodser. See the FAQ in the wiki for more information about the project
https://github.com/haveno-dex/haveno/wiki/FAQ
Haveno is still work in progress. There are no binaries available at this stage. If you want to test Haveno you have to compile it first (see https://github.com/haveno-dex/haveno/blob/master/docs/installing.md).
Status of the project
At the moment Haveno is only a Proof of Concept. It's already possible to initiate crypto <-> XMR and fiat <-> XMR trades, but the platform still needs a lot of work before being available for public use.
💰📊In the past 24 hours, Ethereum whales have purchased more than 110,000 ETH valued at $341 million!💵😮
#Cryptoenthusiast
#Cryptocurrencies
#Cryptowallet
💰📊In the past 24 hours, Ethereum whales have purchased more than 110,000 ETH valued at $341 million!💵😮
#Cryptoenthusiast
#Cryptocurrencies
#Cryptowallet
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⚠️#Google here gave the holder of #cryptocurrencies a dose of anxiety with the news that quantum computers will be able to hack the military-technical cooperation network much earlier than current forecasts.
⚠️ To #crack RSA encryption, you need 20 times less resources than expected (less than 1 million qubits). Modern quantum computers are much weaker, but their power is constantly progressing. According to various forecasts, it will be possible to cross the 1 million cubic meter mark after 2030.👀
💰The Top Ten Cryptocurrencies
1. Bitcoin
2. Ethereum
3. Ripple
Bitcoin jumped back up over the $8,000 dollar mark on 13 April 2018. As this infographic shows, while #Bitcoin is by no means alone in the world of #CryptoCurrencies, it is by far the most valuable #CryptoCurrency, with a total market cap of over $133 billion.
According to figures from CoinMarketCap, #Ethereum is the closest alternative, but with only $49 billion.
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❓ Do you own any cryptocurrency?
👍🏻 Yes
🤔 Not yet, but thinking about buying some
👎🏻 No, and I'm not interested at all