当grep找不到匹配项时，使用grep命令的subprocess.check_输出失败

Question

我试图搜索一个文本文件并检索包含一组特定单词的行。这是我正在使用的代码：

tyrs = subprocess.check_output('grep "^A" %s | grep TYR' % pocket_location, shell = True).split('\n')

当文件包含grep标识的至少一行时，此操作可以正常工作。但是当grep没有标识任何行时，grep返回exit status 1，我得到以下错误：

Traceback (most recent call last):
  File "../../Python_scripts/cbs_wrapper2.py", line 324, in <module>
    tyrs = subprocess.check_output('grep "^ATOM" %s | grep TYR' % pocket_location, shell = True).split('\n')
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/subprocess.py", line 544, in check_output
    raise CalledProcessError(retcode, cmd, output=output)
subprocess.CalledProcessError: Command 'grep "^ATOM" cbsPrediction_files/1u9c_clean/1u9c_clean_fpocket_out/pockets/pocket0_atm.pdb | grep TYR' returned non-zero exit status 1

我怎样才能避免这个问题？我只希望subprocess.check_output在grep找不到任何内容时返回空字符串。

谢谢

Answer 1

tyrs = subprocess.check_output('grep "^A" %s | grep TYR || true' % pocket_location, shell = True).split('\n')