What is the best way in xonsh to loop over the lines of a file?

Question

What is the best way in the xonsh shell to loop over the lines of a text file?

(A) At the moment I'm using

for l in !(cat file.txt): 
    line = l.strip()
    # Do something with line...

(B) Of course, there is also

with open(p'file.txt') as f:
    for l in f:
        line = l.strip()
        # Do something with line...

I use (A) because it is shorter, but is there anything even more concise? And preferably folding the l.strip() into the loop?

Note: My main interest is conciseness (in the sense of a small character count) - maybe using xonsh's special syntax features if that helps the cause.

score 2 · Answer 1 · edited Nov 12 '18 at 01:30

2

You can fold str.strip() into the loop with map():

(A):

for l in map(str.strip, !(cat file.txt)):
    # Do something with line...

(B):

with open('file.txt') as f:
    for l in map(str.strip, f):
        # Do something with l..

edited Nov 12 '18 at 01:30

halloleo

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answered Nov 12 '18 at 00:55

RoadRunner

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Yes, both versions work. I have just tested them in xonsh 0.8.3. – halloleo Nov 12 '18 at 02:39

score 1 · Answer 2 · edited Nov 14 '18 at 00:56

1

Minimal character count could even involve relying on your python implementation to release the file at the end of execution, rather than doing it explicitly:

for l in map(str.strip, open('file.txt')):
    # do stuff with l

Or using the p'' string to make a path in xonsh (this does properly close the file):

for l in p'file.txt'.read_text().splitlines():
    # do stuff with l

splitlines() already removes the new line characters, but not other whitespace.

edited Nov 14 '18 at 00:56

halloleo

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answered Nov 12 '18 at 01:27

soundstripe

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True...I misinterpreted your need for conciseness as a need for readability. – soundstripe Nov 12 '18 at 02:59
Edited my response for brevity in code. Note that CPython will auto-close your file at program exit but other Python implementations may not. – soundstripe Nov 12 '18 at 14:34
Wow, the version with the p'' notation looks now pretty compelling to me. Thx. – halloleo Nov 13 '18 at 11:18
Just realised that the method on `Path` objects is called `read_text`, not `get_text`. Edited the answer accordingly. – halloleo Nov 14 '18 at 00:58

What is the best way in xonsh to loop over the lines of a file?

2 Answers2