blocks|key|685670|text|环境变量必须是字符串，因此使用|type|unstyled|depth|inlineStyleRanges|entityRanges|data|685671|os.environ["DEBUSSY"]+=+"1"|code-block|syntax|javascript|685672|将变量DEBUSSY设置为字符串1。|offset|length|style|CODE|685673|要稍后访问此变量，只需使用：|685674|print(os.environ["DEBUSSY"])|685675|子进程自动继承父进程的环境变量--您无需执行任何特殊操作。|685676|entityMap^0|0|0|3|7|G|1|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|W|8|@$I|X|J|Y|K|L]|$I|Z|J|10|K|L]]|9|@]|A|$]]|$1|M|3|N|5|6|7|11|8|@]|9|@]|A|$]]|$1|O|3|P|5|D|7|12|8|@]|9|@]|A|$E|F]]|$1|Q|3|R|5|6|7|13|8|@]|9|@]|A|$]]|$1|S|3|-4|5|6|7|14|8|@]|9|@]|A|$]]]|T|$]]

Environment variables must be strings, so use

<pre><code>os.environ["DEBUSSY"] = "1"
</code></pre>

to set the variable <code>DEBUSSY</code> to the string <code>1</code>.

To access this variable later, simply use:

<pre><code>print(os.environ["DEBUSSY"])
</code></pre>

Child processes automatically inherit the environment variables of the parent process -- no special action on your part is required.

blocks|key|902286|text|您可能需要考虑代码健壮性的一些其他方面；|type|unstyled|depth|inlineStyleRanges|entityRanges|data|902287|将整数值变量存储为环境变量时，请尝试|902288|os.environ['DEBUSSY']+=+str(myintvariable)|code-block|syntax|javascript|902289|然后，对于检索，考虑到为了避免错误，您应该尝试|902290|os.environ.get('DEBUSSY',+'Not+Set')|902291|可能用'-1‘代替'Not+Set’|902292|所以，把所有这些放在一起|902293|myintvariable+=+1
os.environ['DEBUSSY']+=+str(myintvariable)
strauss+=+int(os.environ.get('STRAUSS',+'-1'))
#+NB+KeyError+<=>+strauss+=+os.environ['STRAUSS']
debussy+=+int(os.environ.get('DEBUSSY',+'-1'))

print+"%25s+%25u,+%25s+%25u"+%25+('Strauss',+strauss,+'Debussy',+debussy)|902294|entityMap^0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|V|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|W|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|X|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|Y|8|@]|9|@]|A|$G|H]]|$1|M|3|N|5|6|7|Z|8|@]|9|@]|A|$]]|$1|O|3|P|5|6|7|10|8|@]|9|@]|A|$]]|$1|Q|3|R|5|F|7|11|8|@]|9|@]|A|$G|H]]|$1|S|3|-4|5|6|7|12|8|@]|9|@]|A|$]]]|T|$]]

You may need to consider some further aspects for code robustness;

when you're storing an integer-valued variable as an environment variable, try

<pre><code>os.environ['DEBUSSY'] = str(myintvariable)
</code></pre>

then for retrieval, consider that to avoid errors, you should try

<pre><code>os.environ.get('DEBUSSY', 'Not Set')
</code></pre>

possibly substitute '-1' for 'Not Set'

so, to put that all together

<pre><code>myintvariable = 1
os.environ['DEBUSSY'] = str(myintvariable)
strauss = int(os.environ.get('STRAUSS', '-1'))
# NB KeyError &lt;=&gt; strauss = os.environ['STRAUSS']
debussy = int(os.environ.get('DEBUSSY', '-1'))

print "%s %u, %s %u" % ('Strauss', strauss, 'Debussy', debussy)
</code></pre>

blocks|key|902222|text|那os.environ["DEBUSSY"]+=+'1'呢？环境变量始终是字符串。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|902223|entityMap^0|1|R|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|K|8|@]|D|@]|E|$]]]|G|$]]

What about <code>os.environ["DEBUSSY"] = '1'</code>? Environment variables are always strings.

blocks|key|685882|text|您应该将字符串值分配给环境变量。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|685883|os.environ["DEBUSSY"]+=+"1"|offset|length|style|CODE|685884|如果想要读取或打印环境变量，只需使用|685885|print+os.environ["DEBUSSY"]|685886|此更改仅对分配它的当前进程有效，不会永久更改该值。子进程将自动继承父进程的环境。|685887|​|685888|📷|atomic|685889|685890|entityMap|0|IMAGE|mutability|IMMUTABLE|imageUrl|https://ask.qcloudimg.com/http-save/yehe-900000/4cfb621a71c67b9a8cc8e818a2445daf.png|imageAlt^0|0|0|R|0|0|0|R|0|0|0|0|1|0|0|0^^$0|@$1|2|3|4|5|6|7|12|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|13|8|@$D|14|E|15|F|G]]|9|@]|A|$]]|$1|H|3|I|5|6|7|16|8|@]|9|@]|A|$]]|$1|J|3|K|5|6|7|17|8|@$D|18|E|19|F|G]]|9|@]|A|$]]|$1|L|3|M|5|6|7|1A|8|@]|9|@]|A|$]]|$1|N|3|O|5|6|7|1B|8|@]|9|@]|A|$]]|$1|P|3|Q|5|R|7|1C|8|@]|9|@$D|1D|E|1E|1|1F]]|A|$]]|$1|S|3|O|5|6|7|1G|8|@]|9|@]|A|$]]|$1|T|3|-4|5|6|7|1H|8|@]|9|@]|A|$]]]|U|$V|$5|W|X|Y|A|$Z|10|11|-4]]]]

You should assign string value to environment variable. 

<code>os.environ["DEBUSSY"] = "1"</code>

If you want to read or print the environment variable just use 

<code>print os.environ["DEBUSSY"]</code> 

This changes will be effective only for the current process where it was assigned, it will no change the value permanently. The child processes will automatically inherit the environment of the parent process. 

<a href="https://i.stack.imgur.com/IHzb3.png"><img src="https://i.stack.imgur.com/IHzb3.png" alt="enter image description here"></a>

blocks|key|902353|text|您可以使用os.environ字典来访问环境变量。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|902354|现在，我遇到的一个问题是，如果我尝试使用os.system运行一个设置环境变量的批处理文件(在**.bat*文件中使用SET命令)，它实际上不会为您的python环境(而是为使用os.system函数创建的子进程)设置它们。要在python环境中实际设置变量，我使用以下脚本：|902355|import+re
import+system
import+os

def+setEnvBat(batFilePath,+verbose+=+False):
++++SetEnvPattern+=+re.compile("set+(\w%2B)(?:=)(.*)$",+re.MULTILINE)
++++SetEnvFile+=+open(batFilePath,+"r")
++++SetEnvText+=+SetEnvFile.read()
++++SetEnvMatchList+=+re.findall(SetEnvPattern,+SetEnvText)

++++for+SetEnvMatch+in+SetEnvMatchList:
++++++++VarName=SetEnvMatch[0]
++++++++VarValue=SetEnvMatch[1]
++++++++if+verbose:
++++++++++++print+"%25s=%25s"%25(VarName,VarValue)
++++++++os.environ[VarName]=VarValue|code-block|syntax|javascript|902356|entityMap^0|5|A|0|K|9|2H|9|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|R|8|@$9|S|A|T|B|C]|$9|U|A|V|B|C]]|D|@]|E|$]]|$1|H|3|I|5|J|7|W|8|@]|D|@]|E|$K|L]]|$1|M|3|-4|5|6|7|X|8|@]|D|@]|E|$]]]|N|$]]

You can use the <code>os.environ</code> dictionary to access your environment variables. 

Now, a problem I had is that if I tried to use <code>os.system</code> to run a batch file that sets your environment variables (using the SET command in a **.bat* file) it would not really set them for your python environment (but for the child process that is created with the <code>os.system</code> function). To actually get the variables set in the python environment, I use this script:

<pre><code>import re
import system
import os

def setEnvBat(batFilePath, verbose = False):
 SetEnvPattern = re.compile("set (\w+)(?:=)(.*)$", re.MULTILINE)
 SetEnvFile = open(batFilePath, "r")
 SetEnvText = SetEnvFile.read()
 SetEnvMatchList = re.findall(SetEnvPattern, SetEnvText)

 for SetEnvMatch in SetEnvMatchList:
 VarName=SetEnvMatch[0]
 VarValue=SetEnvMatch[1]
 if verbose:
 print "%s=%s"%(VarName,VarValue)
 os.environ[VarName]=VarValue
</code></pre>

blocks|key|902448|text|当您使用环境变量(添加/修改/删除变量)时，一个好的做法是在函数完成时恢复以前的状态。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|902449|您可能需要使用本question中描述的modified_environ上下文管理器来恢复环境变量。|offset|length|style|CODE|902450|经典用法：|902451|with+modified_environ(DEBUSSY="1"):
++++call_my_function()|code-block|syntax|javascript|902452|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/a/34333710/1513933^0|0|K|G|8|8|0|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|X|8|@$D|Y|E|Z|F|G]]|9|@$D|10|E|11|1|12]]|A|$]]|$1|H|3|I|5|6|7|13|8|@]|9|@]|A|$]]|$1|J|3|K|5|L|7|14|8|@]|9|@]|A|$M|N]]|$1|O|3|-4|5|6|7|15|8|@]|9|@]|A|$]]]|P|$Q|$5|R|S|T|A|$U|V]]]]

When you play with environment variables (add/modify/remove variables), a good practice is to restore the previous state at function completion.

You may need something like the <code>modified_environ</code> context manager describe in this <a href="https://stackoverflow.com/a/34333710/1513933">question</a> to restore the environment variables.

Classic usage:

<pre><code>with modified_environ(DEBUSSY="1"):
 call_my_function()
</code></pre>

blocks|key|902505|text|如果环境中不存在新变量，则使用setdefault函数设置该变量。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|902506|确保将环境变量设置为字符串，而不是int。否则将抛出TypeError。|902507|import+os

if+not+os.environ.get("DEBUSSY"):
++++os.environ.setdefault("DEBUSSY","1")
else:
+++++os.environ["DEBUSSY"]+=+"1"

print(os.environ["DEBUSSY"])|code-block|syntax|javascript|902508|entityMap^0|F|A|0|Q|9|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|R|8|@$9|S|A|T|B|C]]|D|@]|E|$]]|$1|H|3|I|5|J|7|U|8|@]|D|@]|E|$K|L]]|$1|M|3|-4|5|6|7|V|8|@]|D|@]|E|$]]]|N|$]]

Use <code>setdefault</code> function to set a new variable if the variable does not exist in the environment.
make sure you set the environment variable as a string, not int. Otherwise will throw <code>TypeError</code>.
<pre><code>import os

if not os.environ.get(&quot;DEBUSSY&quot;):
 os.environ.setdefault(&quot;DEBUSSY&quot;,&quot;1&quot;)
else:
 os.environ[&quot;DEBUSSY&quot;] = &quot;1&quot;

print(os.environ[&quot;DEBUSSY&quot;])

</code></pre>

blocks|key|686059|text|有一个很好的开箱即用的Python解决方案，叫做pycrosskit。它将创建对Linux和Windows都是持久的环境变量。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|686060|用法：|686061|#+Will+Set+Persistent+Value+for+Variable+in+System
#+*+subkey+works+only+for+windows+like+file+in+folder
#+*+reg_path+works+only+for+windows+as+register+path+
SysEnv.set_var(name,+value,+subkey,+reg_path=default_reg_path)

#+Will+Get+Persistent+Value+for+Variable+in+System
#+*+reg_path+works+only+for+windows+as+register+path
#+*+delete,+deletes+key+from+environment+and+its+subkeys+after+read
SysEnv.get_var(name,+reg_path=default_reg_path,+delete=False)|code-block|syntax|javascript|686062|entityMap|0|LINK|mutability|MUTABLE|url|https://pypi.org/project/pycrosskit/^0|O|A|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@$A|T|B|U|1|V]]|C|$]]|$1|D|3|E|5|6|7|W|8|@]|9|@]|C|$]]|$1|F|3|G|5|H|7|X|8|@]|9|@]|C|$I|J]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|C|$]]]|L|$M|$5|N|O|P|C|$Q|R]]]]

There is good out of the box Python solution called <a href="https://pypi.org/project/pycrosskit/" rel="nofollow noreferrer">pycrosskit</a>.
It will create environment variables that are persistent both for Linux and Windows.
Usage:
<pre><code># Will Set Persistent Value for Variable in System
# * subkey works only for windows like file in folder
# * reg_path works only for windows as register path 
SysEnv.set_var(name, value, subkey, reg_path=default_reg_path)

# Will Get Persistent Value for Variable in System
# * reg_path works only for windows as register path
# * delete, deletes key from environment and its subkeys after read
SysEnv.get_var(name, reg_path=default_reg_path, delete=False)
</code></pre>

blocks|key|902644|text|我写了这个小context+manager，它只在缩进块的持续时间内设置变量：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|902645|import+os
from+contextlib+import+contextmanager

@contextmanager
def+extended_env(new_env_vars):
++++old_env+=+os.environ.copy()
++++os.environ.update(new_env_vars)
++++yield
++++os.environ.clear()
++++os.environ.update(old_env)|code-block|syntax|javascript|902646|示例用法(适用于Windows的%25和适用于Linux的$+)：|style|CODE|902647|import+subprocess

subprocess.run("echo+$ENVTEST+%25ENVTEST%25",+shell=True)

with+extended_env({"ENVTEST":+"17"}):
++++subprocess.run("echo+$ENVTEST+%25ENVTEST%25",+shell=True)

subprocess.run("echo+$ENVTEST+%25ENVTEST%25",+shell=True)|902648|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/a/3693785/2111778^0|6|F|0|0|0|G|1|R|1|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@$A|X|B|Y|1|Z]]|C|$]]|$1|D|3|E|5|F|7|10|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|11|8|@$A|12|B|13|K|L]|$A|14|B|15|K|L]]|9|@]|C|$]]|$1|M|3|N|5|F|7|16|8|@]|9|@]|C|$G|H]]|$1|O|3|-4|5|6|7|17|8|@]|9|@]|C|$]]]|P|$Q|$5|R|S|T|C|$U|V]]]]

I wrote this little <a href="https://stackoverflow.com/a/3693785/2111778">context manager</a> which sets variables for the duration of an indented block only:
<pre><code>import os
from contextlib import contextmanager

@contextmanager
def extended_env(new_env_vars):
 old_env = os.environ.copy()
 os.environ.update(new_env_vars)
 yield
 os.environ.clear()
 os.environ.update(old_env)
</code></pre>
Example usage (with <code>%</code> for Windows and <code>$</code> for Linux):
<pre><code>import subprocess

subprocess.run(&quot;echo $ENVTEST %ENVTEST%&quot;, shell=True)

with extended_env({&quot;ENVTEST&quot;: &quot;17&quot;}):
 subprocess.run(&quot;echo $ENVTEST %ENVTEST%&quot;, shell=True)

subprocess.run(&quot;echo $ENVTEST %ENVTEST%&quot;, shell=True)
</code></pre>

I need to set some environment variables in the Python script and I want all the other scripts that are called from Python to see the environment variables' set.
If I do,
<pre><code>os.environ[&quot;DEBUSSY&quot;] = 1
</code></pre>
it complains saying that <code>1</code> has to be a string.
I also want to know how to read the environment variables in Python (in the latter part of the script) once I set it.

How to set environment variables in Python?

Windows

Python

Linux

我需要在Python脚本中设置一些环境变量，我希望从Python调用的所有其他脚本都能看到环境变量的设置。如果我这么做了os.environ["DEBUSSY"] = 1它抱怨说1必须是一个字符串。我还想知道如何在设置Python (在脚本的后半部分)中读取环境变量。

问如何在Python中设置环境变量？
EN

回答 9

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问如何在Python中设置环境变量？EN

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