Python subprocess "object has no attribute 'fileno'" error

Question

This code generates "AttributeError: 'Popen' object has no attribute 'fileno'" when run with Python 2.5.1

Code:

def get_blame(filename): 
    proc = []
    proc.append(Popen(['svn', 'blame', shellquote(filename)], stdout=PIPE))
    proc.append(Popen(['tr', '-s', r"'\040'"], stdin=proc[-1]), stdout=PIPE)
    proc.append(Popen(['tr', r"'\040'", r"';'"], stdin=proc[-1]), stdout=PIPE)
    proc.append(Popen(['cut', r"-d", r"\;", '-f', '3'], stdin=proc[-1]), stdout=PIPE)
    return proc[-1].stdout.read()

Stack:

function walk_folder in blame.py at line 55
print_file(os.path.join(os.getcwd(), filename), path)

function print_file in blame.py at line 34
users = get_blame(filename)

function get_blame in blame.py at line 20
proc.append(Popen(['tr', '-s', r"'\040'"], stdin=proc[-1]), stdout=PIPE)

function __init__ in subprocess.py at line 533
(p2cread, p2cwrite,

function _get_handles in subprocess.py at line 830
p2cread = stdin.fileno()

This code should be working the python docs describe this usage.

Answer 1

Three things

First, your ()'s are wrong.

Second, the result of subprocess.Popen() is a process object, not a file.

proc = []
proc.append(Popen(['svn', 'blame', shellquote(filename)], stdout=PIPE))
proc.append(Popen(['tr', '-s', r"'\040'"], stdin=proc[-1]), stdout=PIPE)

The value of proc[-1] isn't the file, it's the process that contains the file.

proc.append(Popen(['tr', '-s', r"'\040'"], stdin=proc[-1].stdout, stdout=PIPE))

Third, don't do all that tr and cut junk in the shell, few things could be slower. Write the tr and cut processing in Python -- it's faster and simpler.