Python3 - Store stdout into an array variable

Question

I have a Python script, that converts PDF content to a string.

text = list();

#npages is number of pages in the PDF file.
for n in range(npages):
    text[n] = os.system('pdftotext myfile.pdf -') #the "-" prints to stdout.

print(text)

However when I print text, this is the output (a PDF file with two pages):

{0: 0, 1: 0}

When running the script, I see the os.system output being sent to the command line:

text from myfile.pdf page 1
text from myfile.pdf page 2

How can I store the standard output from the pdftotext command in a list?

But you create a dictionary at line 1? Is it list or dictionary? — Wimanicesir
– Wimanicesir, Commented May 21, 2019 at 10:12
① if text were a list, you will receive an IndexError when you try to access the non-existing element text[0] ② at every iteration you are receiving the whole text of the PDF file, not just the text of an individual page. Very sloppy question. — gboffi
– gboffi, Commented May 21, 2019 at 10:26

knh190 · Accepted Answer · 2019-05-21 10:30:23Z

4

You are not receiving command line outputs, only the returned system code. Generally 0 is for success, which means your commands for npages 0 and 1 were successful.

You may use subprocess and redirect output to your Python script. A shorthand for this is:

import subprocess

out = subprocess.check_output(['ls', '-lh']) # example
print(out)

To accept the short - you'll need to use subprocess.Popen(bufsize=0). This should work:

cmd = ['pdftotext', 'myfile.pdf', '-']
proc = subprocess.Popen(cmd, stdout=subprocess.PIPE, bufsize=0)
# get output and error
out, err = proc.communicate()

print(out)

edited May 21, 2019 at 10:30

answered May 21, 2019 at 10:12

knh190

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6 Comments

oliverbj Over a year ago

I am a little confused on how/where to use the subprocess for pdftotext call. If I do: text[n] = subprocess.check_output('pdftotext myfile.pdf -) I get the following error: FileNotFoundError: [Errno 2] No such file or director: 'pdftotext myfile.pdf -'

knh190 Over a year ago

@oliverbj check doc first, before you ask! It should be subprocess.check_output(['pdftotext', 'myfile.pdf', '-']) which only accepts commands in a list.

gboffi Over a year ago

@oliverbj In the answer the argument to check_output is a list of strings, in your comment it is a string. Maybe is this difference the reason way of your erros?

knh190 Over a year ago

@oliverbj Looks like it's caused by the last -. You'll need subprocess.Popen for that. I'll update my answer.

oliverbj Over a year ago

@knh190 - I just tried doing subprocess.check_output(['pdftotext', 'myfile.pdf', '-']) - but that returns with an error code of 99. I also tried removing the - part.

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