How to pass a variable to subprocess.Popen.stdin.write() in Python

Question

I am using Popen from subprocess library and wish to pass a variable to popen.stdin.write for executing a bat file. I wish to execute my bat file by

C:\Users\7zx3we\test.bat chinni

Mycode


from subprocess import Popen,PIPE

p = Popen('cmd.exe ', stdin=PIPE, stdout=PIPE)
name = 'chinni'
p.stdin.write('C:\Users\7zx3we\test.bat ' + name + '\n')

But this is giving me a syntax error and failing to run. What can I try to resolve that?

Best to include (verbatim) any errors you get with your question but you'd probably need to use raw strings, e.g., `r'C:\Users\7zx3we\test.bat '` since the `'\t'` is a tab character. — , Mar 03 '21 at 14:21
Additionally (next to @JustinEzequiel 's comment), you're only importing `Popen`, but you'll also need to import `PIPE` from `subprocess` — Giuseppe Accaputo, Mar 03 '21 at 14:23

Giuseppe Accaputo · Answer 1 · 2021-03-03T16:27:12.270

Two things:

You need to define the encoding if you want to open stdin in text mode. You can do this by specifying the encoding parameter:

Popen('cmd.exe`, stdin=PIPE, stdout=PIPE, encoding='utf8')

You need to escape the backslashes in the path, since otherwise they will be evaluated to a wrong value, e.g., \U starts a Unicode escape sequence and \t is the tab character:

p.stdin.write('C:\\Users\\7zx3we\\test.bat ' + name)

How to pass a variable to subprocess.Popen.stdin.write() in Python

1 Answers1