python - Why is this else: pass needed for processing to continue? -

python - Why is this else: pass needed for processing to continue? -

can explain why else:pass shown below needed in order rest of code (the final print 'processing... statement) executed? note print in else set there tell execution indeed taking path.

it seems should happen whenever continue isn't executed since code in else nothing. however, if leave else out, nil farther in for loop appears executed when status false -- when files extension do exist in directory -- doesn't create sense me. docs continue "continues next cycle of nearest enclosing loop", fine, if 1 not executed, shouldn't processing should proceed next statement?

import os source_dir = r'c:\downloads' ext = '.mp3' dirname, subdirlist, filelist in os.walk(source_dir): if not any(os.path.splitext(filename)[1].lower() == ext filename in filelist): print ' skipping "{}"'.format(dirname) go on else: # why clause needed go on iteration of loop? print 'contains "{}"'.format(dirname) pass print 'processing "{}" has "{}" files'.format(dirname, ext)

mystery solved

the seemingly unusual behavior due indentation problem not visible in code above nor in text editor. turned out lastly print statement indented 3 spaces tab, makes appear align else, in fact either follows pass in else if it's there, or follows continue in first part of if. confusing me great deal.

here's screenshot of code in text editor "show space/tabs" alternative turned on. reddish dots represent spaces , reddish >> represents tab character:

you don't need it. ran next 2 scripts:

#test1.py import os source_dir = '.' ext = '.txt' dirname, subdirlist, filelist in os.walk(source_dir): if not any(os.path.splitext(filename)[1].lower() == ext filename in filelist): print ' skipping "{}"'.format(dirname) go on else: # why clause needed go on iteration of loop? print 'contains "{}"'.format(dirname) pass print 'processing "{}" has "{}" files'.format(dirname, ext)

and

#test2.py import os source_dir = '.' ext = '.txt' dirname, subdirlist, filelist in os.walk(source_dir): if not any(os.path.splitext(filename)[1].lower() == ext filename in filelist): print ' skipping "{}"'.format(dirname) go on #else: # why clause needed go on iteration of loop? # print 'contains "{}"'.format(dirname) # pass print 'processing "{}" has "{}" files'.format(dirname, ext)

i ran them as:

python test1.py > junk.log python test2.py > junk.log2

here's first couple lines of junk.log:

test $ head junk.log processing "." has ".txt" files skipping "./new" skipping "./unum" processing "./unum/kiv-unum-409befe069ac" has ".txt" files skipping "./unum/kiv-unum-409befe069ac/build" skipping "./unum/kiv-unum-409befe069ac/build/bdist.macosx-10.3-fat" skipping "./unum/kiv-unum-409befe069ac/build/lib" skipping "./unum/kiv-unum-409befe069ac/build/lib/tests" skipping "./unum/kiv-unum-409befe069ac/build/lib/unum" skipping "./unum/kiv-unum-409befe069ac/build/lib/unum/units

notice presence of "processing" lines.

then diff output:

diff junk.log junk.log2

with next results:

0a1 > contains "." 3a5 > contains "./unum/kiv-unum-409befe069ac" 14a17 > contains "./unum/kiv-unum-409befe069ac/docs" 16a20 > contains "./unum/kiv-unum-409befe069ac/nose-1.2.1-py2.7.egg/egg-info" 19a24 > contains "./unum/kiv-unum-409befe069ac/nose-1.2.1-py2.7.egg/nose" 30a36 > contains "./unum/kiv-unum-409befe069ac/unum.egg-info"

note there no differences on "processing" lines.

python python-2.7 if-statement continue