Useful python snippets like using shell, command line args

asterisk.py

# *list expands the list elements as positional arguments print(*[1,2,3]) = print(1,2,3)

l1 = [4, 7, 8]
l2 = ["a", "b", "c"]

zl = list(zip(l1, l2))

print(zl)

l1_rec, l2_rec = zip(*zl)

print(l1_rec)
print(l2_rec)

print(dict(zip(l1, l2)))


# val_last has to be kwarg
# val can't be kwarg as it is just before *arg
def func(val, *val_args, val_last, **key_args):
    return (val, val_args, val_last, key_args)


print(func(10, 2, 3, id=1, val_last=5, key=3))
print(func(2, 3, 5, val_last=7, id=1, key=3, dummy=400))

first, *mid, last = [1, 2, 3, 4]
print(first, mid, last)


def foo(x, y, z):
    print("x=" + str(x))
    print("y=" + str(y))
    print("z=" + str(z))


mydict = {"x": 1, "z": 3, "y": 2}

foo(**mydict)  # maps dict to paramaters

cmd-args-with-options.py

from argparse import ArgumentParser

parser = ArgumentParser()
parser.add_argument("-f", "--file", dest="filename",
                    help="write report to FILE", metavar="FILE")
parser.add_argument("-o", "--option", dest="option",
                    help="option value")
parser.add_argument("-q", "--quiet",
                    action="store_false", dest="verbose", default=True,
                    help="don't print status messages to stdout")

args = parser.parse_args()

print(args.filename)
print(args.option)

cmd-args.py

#!/usr/bin/python3  
import sys  

print('Number of arguments:', len(sys.argv), 'arguments.') 
print('Argument List:', str(sys.argv))

Python-Snippets.py

print("------")

shell-pipe.py

from subprocess import Popen, PIPE

command = "find . -name '*.py' | sed 's/\.\///' | sort"

for filename in Popen(command, shell=True, stdout=PIPE).stdout:
    print(filename.decode("utf-8").strip()) # default is in utf-8 encoded, strip to remove trailing newlines