I have
cmd = subprocess.Popen('dir',shell=True,stdout=subprocess.PIPE)
for line in cmd.stdout:
columns = line.split(' ')
print (columns[3])
have error in line 3 Type Str doesnt support the buffer API.
What am i doing wrong i am on Python 3.3
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3 Answers
You are reading binary data, not str, so you need to decode the output first. If you set the universal_newlines argument to True, then stdout is automatically decoded using the result of the locale.getpreferredencoding() method
(same as for opening text files):
cmd = subprocess.Popen(
'dir', shell=True, stdout=subprocess.PIPE, universal_newlines=True)
for line in cmd.stdout:
columns = line.decode().split()
if columns:
print(columns[-1])
If you use Python 3.6 or newer, you can use an explicit encoding argument for to the Popen() call to specify a different codec to use, like, for example, UTF-8:
cmd = subprocess.Popen(
'dir', shell=True, stdout=subprocess.PIPE, encoding='utf8')
for line in cmd.stdout:
columns = line.split()
if columns:
print(columns[-1])
If you need to use a different codec in Python 3.5 or earlier, don't use universal_newlines, just decode text from bytes explicitly.
You were trying to split a bytes value using a str argument:
>>> b'one two'.split(' ')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: Type str doesn't support the buffer API
By decoding you avoid that problem, and your print() call will not have to prepend the output with b'..' either.
However, you probably just want to use the os module instead to get filesystem information:
import os
for filename in os.listdir('.'):
print(filename)
answered Apr 4, 2013 at 17:09
Martijn Pieters
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8 Comments
Nick Loach
Thanks it works but any idea why i am getting list index out of range error
Martijn Pieters
@NickLoach: the line has fewer than 3 columns?
Nick Loach
Thanks Martijn the line has ['03-04-2013', '', '19:48', '', '', '', '<DIR>', '', '', '', '', '', '', '', '', '', '.ipython\r\n'] i want the feild called .ipython as output
Martijn Pieters
Why not use
os.listdir() instead?Nick Loach
I made a simple example the command i would be running will not be a os command but a binary that outputs something on the above lines
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A simpler solution of the first part of Martijn Pieters's answer is to pass the universal_newlines=True argument to the Popen call.
I would even simplify this to:
output = subprocess.check_output('dir', universal_newlines=True)
columns = output.split()
print(columns)
NOTE: If file or directory names contain spaces, use os.listdir('.') as suggested in Martijn Pieters's answer or something like the following:
output = subprocess.check_output('dir', universal_newlines=True)
columns = []
for e in output.split():
if len(columns) > 0 and columns[-1].endswith('\\'):
columns[-1] = columns[-1][:-1] + " " + e
else:
columns.append(e)
print(columns)
4 Comments
jfs
dir is an internal command on Windows i.e., if there is no dir.exe then shell=True is necessary in this case.jfs
If we assume one-column output then you could use
.splitlines(), to handle paths with spaces
tjanez
@J.F.Sebastian, agreed. I didn't use
.splitlines() since my version of dir (GNU coreutils) 8.21 produces output in multiple columns.jfs
dir produces a single column output if stdout is redirected (as it is the case with stdout=PIPE). Try dir | cat, to see it in the terminalBetter use binascii.b2a_uu that converts binary data to a line of ASCII characters
from binascii import b2a_uu
cmd = b2a_uu(subprocess.Popen('dir',shell=True,stdout=subprocess.PIPE))
