How to make an activation flag?

[Krszt]

Hello,
I have a program, which runs well.
It looks like

os.chdir('zips')
a = open("ziplist.txt", "w")
for path, subdirs, files in os.walk(r'./'):
    for filename in files:
        if filename.endswith(".zip"):
            commands....
            for line in open('%s.txt' % (date_ID)).readlines():
                if line.startswith('range_samples:'):
                    commands...
                    os.chdir('../')

Now I want to expand it with an if/else statement as an activation flag, something like: if the first argv is 1, run the whole program written above
and else do nothing.

I am trying it like this:

if activate_flag == 1 :
    os.chdir('zips')
    a = open("ziplist.txt", "w")
    for path, subdirs, files in os.walk(r'./'):
        for filename in files:
            if filename.endswith(".zip"):
                commands....
                for line in open('%s.txt' % (date_ID)).readlines():
                    if line.startswith('range_samples:'):
                       commands...
                       os.chdir('../')
else: 
   print("NO")

But it just write out the else statement: NO
Where is my mistake?