bash - Python equivalent to perl -pe?

Question

I need to pick some numbers out of some text files. I can pick out the lines I need with grep, but didn't know how to extract the numbers from the lines. A colleague showed me how to do this from bash with perl:

cat results.txt | perl -pe 's/.+(d.d+).
/1 /'

However, I usually code in Python, not Perl. So my question is, could I have used Python in the same way? I.e., could I have piped something from bash to Python and then gotten the result straight to stdout? ... if that makes sense. Or is Perl just more convenient in this case?

Answer 1

Yes, you can use Python from the command line. python -c <stuff> will run <stuff> as Python code. Example:

python -c "import sys; print sys.path"

There isn't a direct equivalent to the -p option for Perl (the automatic input/output line-by-line processing), but that's mostly because Python doesn't use the same concept of $_ and whatnot that Perl does - in Python, all input and output is done manually (via raw_input()/input(), and print/print()).

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For your particular example:

cat results.txt | python -c "import re, sys; print ''.join(re.sub(r'.+(d.d+).
', r'1 ', line) for line in sys.stdin)"

(Obviously somewhat more unwieldy. It's probably better to just write the script to do it in actual Python.)