Multiline script in a python command line argument

Question

I am trying to invoke python from within an arch linux PKGBUILD script:

python -c "from module import func; func()"

The func raises an exception, which is expected behavior but causes the script to fail. Catching the exception like this does not work:

python -c "from module import func; try: func(); except ValueError: pass"

It seems there is no way to put try/except statements into a single line (Python: try statement in a single line).

Is there another way to ignore the exception or the fact that python returns with an error? A solution that does not require additional scripts or other files would be most welcome :)

This is not about `try/except` but multiline in general; corrected the title :) — Erik Kaplun, Apr 25 '14 at 14:22

score 3 · Accepted Answer · edited Apr 02 '20 at 11:41

3

Strings in shell can contain embedded newlines:

python -c 'from module import func
try:
  func()
except ValueError:
  pass
'

Note that this presents a challenge if the Python to run contains a mix of quotation marks, which would require some contortions to ensure they are all escaped properly. In that case, a here document would be more appropriate then the -c option (although this presents its own issues if the code to run needs to read from standard input.)

python << EOF
from module import func
try:
  func()
except ValueError:
  pass
EOF

edited Apr 02 '20 at 11:41

Stefan Paul Noack

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answered Apr 25 '14 at 14:18

chepner

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Indeed, this works. Makes me feel slightly stupid... well.. +1 :) – MB-F Apr 25 '14 at 14:20

score 0 · Answer 2 · answered Apr 25 '14 at 14:21

0

You can also enter the script to be executed interactively like this:

$ cat -- | python
<code here>
<code here>
<code here>
<press Ctrl-D>

and Python will run what you entered, for example:

~$ cat -- | python
from module import func
try:
  func()
except ValueError:
  pass
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: No module named module

answered Apr 25 '14 at 14:21

Erik Kaplun

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That is not what I need, but still interesting. – MB-F Apr 25 '14 at 14:22
I've changed the example to your code; maybe then it's what you need. – Erik Kaplun Apr 25 '14 at 14:24
The `cat` is unnecessary. You could do `python <<-SCRIPT`, using a heredoc. – kojiro Apr 25 '14 at 14:24
@kojiro: true, but it's not shorter, so the reverse logic also holds. – Erik Kaplun Apr 25 '14 at 14:25
It's not shorter, but it's fewer processes. – kojiro Apr 25 '14 at 14:25
1

Like that matters in 99.9% of the cases. – Erik Kaplun Apr 25 '14 at 14:26
@ErikAllik isn't your example interactive? I need it inside a script. – MB-F Apr 25 '14 at 14:26
If inside of script, then you are right; I missed that bit. – Erik Kaplun Apr 25 '14 at 14:27

Multiline script in a python command line argument

2 Answers2