Python misinterpreting sys.argv[1] when called with * as filename? - python-3.x

Question

I'm doing a task for school where i need my program to do four things:
(1) It should take in a filename as an argument and count lines, words and chars.
(2) It should accept the argument *.py and scan all the .py files in current directory for the same as in (1)
(3) It should accept the argument * and scan ALL files in current directory for the same as in (1).
(4) I should be able to call it from command line as simply filename followed by argument. Example: Filename is Hello_world.py and takes one argument. Then it should look like this:
Hello_world arg
When I call with a specific filename as in (1) it seems to be working here:
else:
a, b, c, n = counting(call)
print('There are: ' + str(a) + ' lines, ' + str(b) + ' words and ' + str(c) + ' chars in ' + n)
but not working for (2) and (3) here:
if call == '*':
import os
for fname in os.listdir(os.getcwd()):
a, b, c, n = counting(fname)
print('There are: ' + str(a) + ' lines, ' + str(b) + ' words and ' + str(c) + ' chars in ' + n)
elif call == '*.py':
import glob
for fname in glob.glob('*.py'):
a, b, c, n = counting(fname)
print('There are: ' + str(a) + ' lines, ' + str(b) + ' words and ' + str(c) + ' chars in ' + n)
I tried printing out sys.argv[1] when using * and *.py as argument and then it prints out the first file in the directory and not * or *.py. Why is python interpreting * as a filename in the directory instead of simply the string *? How do I work around this? I tried moving the imports untill it actually entered the if/elif, but that did no change.
When it comes to making the script callable as in (4) I'm clueless, but that is not my main concern at this moment.
Entire script here:
import sys
def counting(fname):
lines = words = chars = 0
f= open(fname)
for line in f:
lines += 1
words += len(line.split())
chars += len(line)
name = f.name
f.close()
return lines, words, chars, name
def main():
call = sys.argv[1]
print(sys.argv[1])
a = b = c = 0
if call == '*':
import os
for fname in os.listdir(os.getcwd()):
a, b, c, n = counting(fname)
print('There are: ' + str(a) + ' lines, ' + str(b) + ' words and ' + str(c) + ' chars in ' + n)
elif call == '*.py':
import glob
for fname in glob.glob('*.py'):
a, b, c, n = counting(fname)
print('There are: ' + str(a) + ' lines, ' + str(b) + ' words and ' + str(c) + ' chars in ' + n)
else:
a, b, c, n = counting(call)
print('There are: ' + str(a) + ' lines, ' + str(b) + ' words and ' + str(c) + ' chars in ' + n)
if __name__ == '__main__':
main()
All help greatly appreciated. Thanks in advance!

Answer 1

When you run a program like:
prog *
there's no guarantee that the * will make it through to the program unscathed.
In fact, many shells will explicitly doe expansion so that the * gets turned into a number of arguments (such as every file in the current directory, for example).
In fact, you have to go out of your way to prevent this, by escaping special characters so the shell won't interpret them, such as:
prog \*
But. if you want to process all the files anyway, you should probably let the shell do what it wants, then process each of the expanded arguments separately.
In Python, that would be something like:
import sys
for arg in sys.argv[1:]: # [0] is the program name.
print(arg)