Coding Bash vs. Perl vs. Python (by Evan Liu)

Topics about help

Help: how to use help 

In perl, use the below three commands to get helps on inner varaibles,inner functions, and keywords
perldoc -v PerlVar
perldoc -f PerlFunc
perldoc -q FAQKeywords

Tasks:
Bash Perl Python 
  1. #todo

  2. 

  3. -------output----------

  1. #todo

  1. #run in linux shell

  2. #1. perldoc -v PerlVar

  3. perldoc -T -v '$_' |sed -n '/$_ =~/p' |sed 's/^[[:space:]]*//'

  4. 

  5. #2. perldoc -f PerlFunc

  6. perldoc -T -f split | egrep 'split\(' |sed 's/^[[:space:]]*//'

  7. 

  8. #3. perldoc -q FAQKeywords

  9. perldoc -T -q debug | egrep 'Dumper' |sed 's/^[[:space:]]*//'

  10. 

  11. -------output----------

  1. #run in linux shell

  2. #1. perldoc -v PerlVar

  3. $_ =~ /^Subject:/

  4. $_ =~ tr/a-z/A-Z/

  5. 

  6. #2. perldoc -f PerlFunc

  7. print join(':', split('b', 'abc')), "\n";

  8. print join(':', split('', 'abc')), "\n";

  9. print join(':', split(//, 'abc', 1)), "\n";

  10. print join(':', split(//, 'abc', 2)), "\n";

  11. print join(':', split(//, 'abc', 3)), "\n";

  12. print join(':', split(//, 'abc', 4)), "\n";

  13. print join(':', split(',', 'a,b,c,,,')), "\n";

  14. print join(':', split(',', 'a,b,c,,,', -1)), "\n";

  15. ($login, $passwd) = split(/:/);

  16. print join(':', split(/ /, ' abc')), "\n";

  17. print join(':', split(//, ' abc'));

  18. print join(':', split(//, ' abc', -1)), "\n";

  19. split(/-|,/, "1-10,20", 3)

  20. split(/(-|,)/, "1-10,20", 3)

  21. split(/-|(,)/, "1-10,20", 3)

  22. split(/(-)|,/, "1-10,20", 3)

  23. split(/(-)|(,)/, "1-10,20", 3)

  24. 

  25. #3. perldoc -q FAQKeywords

  26. The Data::Dumper module can pretty-print Perl data structures:

  27. use Data::Dumper qw( Dumper );

  28. print STDERR "The hash is " . Dumper( \%hash ) . "\n";

  1. #run in linux shell

  2. #1. list all modules

  3. echo "pydoc modules"

  4. echo "python -c \"help('modules')\""

  5. 

  6. #2. list installed packages

  7. echo "pip list"

  8. 

  9. #3. help about 'sys' module

  10. echo "pydoc sys"

  11. echo "python -c \"help('sys')\""

  12. 

  13. -------output----------

  1. #run in linux shell

  2. #1. list all modules

  3. pydoc modules

  4. python -c "help('modules')"

  5. 

  6. #2. list installed packages

  7. pip list

  8. 

  9. #3. help about 'sys' module

  10. pydoc sys

  11. python -c "help('sys')"

Help: get the module path 

 

Tasks:
1.1. print the path of a module
Bash Perl Python 
  1. #  todo

  2. 

  3. -------output----------

  1. #  todo

  1. #  todo

  2. 

  3. -------output----------

  1. #  todo

  1. import os; os.__file__

  2. import re; print re.__file__

  3. import logging; logging.__file__

  4. import bpython; print bpython.__file__

  5. 

  6. -------output----------

  1. /usr/lib/python2.7/re.pyc

  2. /usr/lib/python2.7/dist-packages/bpython/__init__.pyc

Help: get all functions of a module 


		  
		  

		  
Tasks:

		  

		       
          
          

             
             

		     

                Bash
                Perl
                Python			   
		     

             
              

                
  1. #todo

  2. 

  3. -------output----------



  1. #todo



                
  1. #todo

  2. 

  3. -------output----------



  1. #todo



                
  1. import re

  2. import inspect

  3. print dir(re)

  4. #or use inspect, which is better

  5. print inspect.getmembers(re, inspect.isfunction)

  6. 

  7. -------output----------



  1. ['DEBUG', 'DOTALL', 'I', 'IGNORECASE', 'L', 'LOCALE', 'M', 'MULTILINE', 'S', 'Scanner', 'T', 'TEMPLATE', 'U', 'UNICODE', 'VERBOSE', 'X', '_MAXCACHE', '__all__', '__builtins__', '__doc__', '__file__', '__name__', '__package__', '__version__', '_alphanum', '_cache', '_cache_repl', '_compile', '_compile_repl', '_expand', '_pattern_type', '_pickle', '_subx', 'compile', 'copy_reg', 'error', 'escape', 'findall', 'finditer', 'match', 'purge', 'search', 'split', 'sre_compile', 'sre_parse', 'sub', 'subn', 'sys', 'template']

  2. #or use inspect, which is better 

  3. [('_compile', <function _compile at 0x7f5e2eced1b8>), ('_compile_repl', <function _compile_repl at 0x7f5e2eced230>), ('_expand', <function _expand at 0x7f5e2eced2a8>), ('_pickle', <function _pickle at 0x7f5e2eced398>), ('_subx', <function _subx at 0x7f5e2eced320>), ('compile', <function compile at 0x7f5e2ecf2f50>), ('escape', <function escape at 0x7f5e2eced140>), ('findall', <function findall at 0x7f5e2ecf2e60>), ('finditer', <function finditer at 0x7f5e2ecf2ed8>), ('match', <function match at 0x7f5e2ecf2c08>), ('purge', <function purge at 0x7f5e2eced050>), ('search', <function search at 0x7f5e2ecf2c80>), ('split', <function split at 0x7f5e2ecf2de8>), ('sub', <function sub at 0x7f5e2ecf2cf8>), ('subn', <function subn at 0x7f5e2ecf2d70>), ('template', <function template at 0x7f5e2eced0c8>)]