Using Boolean Flags in Python Click Library (command line arguments)

Question

I'm trying to make a verbose flag for my Python program. Currently, I'm doing this:

import click  #global variable verboseFlag = False  #parse arguments @click.command() @click.option('--verbose', '-v', is_flag=True, help="Print more output.") def log(verbose):     global verboseFlag     verboseFlag = True  def main():         log()             if verboseFlag:          print("Verbose on!")  if __name__ == "__main__":     main() 

It'll never print "Verbose on!" even when I set the '-v' argument. My thoughts are that the log function needs a parameter, but what do I give it? Also, is there a way to check whether the verbose flag is on without global variables?

Answer 1

So click is not simply a command line parser. It also dispatches and processes the commands. So in your example, the log() function never returns to main(). The intention of the framework is that the decorated function, ie: log(), will do the needed work.

Code:

import click  @click.command() @click.option('--verbose', '-v', is_flag=True, help="Print more output.") def log(verbose):     click.echo("Verbose {}!".format('on' if verbose else 'off'))   def main(*args):     log(*args) 

Test Code:

if __name__ == "__main__":     commands = (         '--verbose',         '-v',         '',         '--help',     )      import sys, time      time.sleep(1)     print('Click Version: {}'.format(click.__version__))     print('Python Version: {}'.format(sys.version))     for cmd in commands:         try:             time.sleep(0.1)             print('-----------')             print('> ' + cmd)             time.sleep(0.1)             main(cmd.split())          except BaseException as exc:             if str(exc) != '0' and \                     not isinstance(exc, (click.ClickException, SystemExit)):                 raise 

Results:

Click Version: 6.7 Python Version: 3.6.3 (v3.6.3:2c5fed8, Oct  3 2017, 18:11:49) [MSC v.1900 64 bit (AMD64)] ----------- > --verbose Verbose on! ----------- > -v Verbose on! ----------- >  Verbose off! ----------- > --help Usage: test.py [OPTIONS]  Options:   -v, --verbose  Print more output.   --help         Show this message and exit.