Python: call piped commands using subprocess

For example, I want to call external command:
cat /tmp/fruits.txt | grep apple
, depending on if the input is trusted or not, we have the following two options:
  • For untrusted input:
    import subprocess
    cat = subprocess.popen(['/bin/cat', '/tmp/fruits.txt'], stdout=PIPE)
    grep = subprocess.popen(['/bin/grep', 'apple'], stdin=cat.stdout, stdout=PIPE)
    output = grep.communicate()[0]
    print output
  • For trusted input, you can simply set shell=True:
    import subprocess
    output=subprocess.check_output('cat /tmp/fruits.txt | grep apple', shell=True)
    print output

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