Tips for replacing and debugging functions

When you write a little script, you assemble and execute a string, right?

Something like this (I don't use shutil because it's an example)

os.system('mv %(src)s %(dst)s' % locals())

Such a guy

os.system('ssh %(user)s@%(host)s -p %(port)s hostname' % locals())

So, have you ever done this when you want to check the assembled string? It's a hassle

# os.system('mv %(src)s %(dst)s' % locals())
print 'mv %(src)s %(dst)s' % locals()

If you want to debug like this, it's easier to replace ʻos.system`

def out(s):
  print s

os.system = out
os.system('mv %(src)s %(dst)s' % locals())

Now that ʻos.systemis actuallyprint`, when you run it, the assembled string will be output as standard and you can debug it easily.

By the way, python2 series uses def because print is a sentence, but python3 series is easier because print is an expression.

os.system = print
os.system('mv %(src)s %(dst)s' % locals())

If it is a first-class object language, it will be applied, so it may be good to remember