Python3不采用源命令设置的环境变量

Question

I have written a config file as follows:

bucket_name=some-bucket

I run the command source config_de_local where config_de_local is the file name in which variables to be set are stored.

Then I run the command: echo $bucket_name and I get the o/p: some-bucket . However, the config file is still not able to import any variable, it states all as null. This is how I am importing a variable: bucket_name = os.getenv('bucket_name', '')

However, in the terminal, if I run the command: export bucket_name=some-bucket and then in Python3 shell, I run the line: print(os.getenv('bucket_name','')) I get the desired output.

Note: I am running Python3 in a virtualenv; I activate it and then set my env variables via source and export .

Answer 1

The reason that this isn't working is because un-exported environment variables will only be visible to the current process (which is Bash in your case), but not any child processes (eg Python). An export is indeed necessary or the variable could specifically be specified when running Python like this:

fots ~ $ bucket_name=some-bucket python3
Python 3.7.2 (default, Jan 13 2019, 12:50:01) 
[Clang 10.0.0 (clang-1000.11.45.5)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import os
>>> os.getenv('bucket_name', '')
'some-bucket'

In the case you wish to source them, a simple solution is to export these variables in the script that you source (which will in turn export them in your current shell).

eg

fots ~ $ cat config_de_local
export bucket_name=some-bucket
fots ~ $ source config_de_local
fots ~ $ python3
Python 3.7.2 (default, Jan 13 2019, 12:50:01) 
[Clang 10.0.0 (clang-1000.11.45.5)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import os
>>> os.getenv('bucket_name', '')
'some-bucket'

There are various ways to feed these exported environment variables to your application. A simple shell script wrapping the program would work (as you are doing). This script would activate the virtualenv and then source the file.

Alternatively, if the app is a daemon that runs in the background, creating a systemd or supervisor service would work too as you can also specify environment variables in the service definition.

Hope this helps!
Fotis