分配shell脚本执行结果给变量

Question

我有shell脚本。其中有：

./dtapi get_probability decision_tree simulated_diabetes_incidence_data_new.txt AGE 70 weight 34 height 5.5 sex 0 ds1 34 

现在我试图用python脚本执行此shell脚本并将结果存储到某个变量中。 test.py包含 -

import os, sys 
result = os.system("sh cmd_dtapi.sh") 
print "Result is : ", result 

但它的行为是这样的：

python test.py 
{"risk_of_disease":"2.122e-314"}Result is : 0 

结果得到直接打印，分配需要0。

如何将结果存储到某个变量中？

更新

以下的答案后 -

import subprocess 
import json 
result_process_output = subprocess.check_output("sh cmd_dtapi.sh") 
result_json = json.loads(result_process_output) 
result = result_json["risk_of_disease"] 
print "Result is : ", result  

给人

Traceback (most recent call last): 
    File "test.py", line 3, in <module> 
    result_process_output = subprocess.check_output("sh cmd_dtapi.sh") 
    File "/usr/lib/python2.7/subprocess.py", line 566, in check_output 
    process = Popen(stdout=PIPE, *popenargs, **kwargs) 
    File "/usr/lib/python2.7/subprocess.py", line 710, in __init__ 
    errread, errwrite) 
    File "/usr/lib/python2.7/subprocess.py", line 1327, in _execute_child 
    raise child_exception 
OSError: [Errno 2] No such file or directory 

Answer 1

Here是os.system() despcription：

Execute the command (a string) in a subshell. This is implemented by calling the Standard C function system(), and has the same limitations. Changes to sys.stdin, etc. are not reflected in the environment of the executed command. If command generates any output, it will be sent to the interpreter standard output stream.

这意味着，您的shell将{risk_of_disease":"2.122e-314"}打印到标准输出。

至于os.system()返回0：

On Windows, the return value is that returned by the system shell after running command. The shell is given by the Windows environment variable COMSPEC: it is usually cmd.exe, which returns the exit status of the command run; on systems using a non-native shell, consult your shell documentation.

所以回你的shell脚本的代码为0，并将其分配给result。所以技术上你已经将结果存储在变量中。

@edit：

要解决问题，你需要使用subprocess模块，它允许系统调用的更详细的操作。

import subprocess 
import json 
result_process_output = subprocess.check_output("sh cmd_dtapi.sh", shell=True) 
result_json = json.loads(result_process_output) 
result = result_json["risk_of_disease"] 
print "Result is : ", result