What is sysargv?

[Pedroski55]

(Something has changed here, I can't seem to mark Python code as code. Sorry!)

I was just looking at this, but I cannot understand what  this part really does:

 

n = 100
    if sys.argv[1:]:
        n = int(sys.argv[1])

That is to say, I don't understand the purpose of sys.argv or what exactly this does:

if sys.argv[1:]:

Why would I need the above? Why not just put:
n = 100
for i in range(n, 0, -1) ??
 

def myApp():
    import sys

    n = 100
    if sys.argv[1:]:
        n = int(sys.argv[1])

    def bottle(n):
        if n == 0: return "no more bottles of beer"
        if n == 1: return "one bottle of beer"
        return str(n) + " bottles of beer"

    for i in range(n, 0, -1):
        print(bottle(i), "on the wall,")
        print(bottle(i) + ".")
        print("Take one down, pass it around,")
        print(bottle(i-1), "on the wall.")

[ibreeden]

sys.argv is a list of arguments passed when you start your program. sys.argv[0] is the name of your program. The rest are the parameters.
If your program, say demo.py is:

---

import sys
print(sys.argv)

---

... and you start your program with parameters:

---

./demo.py a b c

---

... then your output will be:

Output:
['./demo.py', 'a', 'b', 'c']

[Pedroski55]

Thanks!

What might I use syargsv for? How is it useful?

[buran]

Thanks!

What might I use syargsv for? How is it useful?

As explained - you can pass CLI arguments when you run your script. Of couse there are libraries that help write better CLI, but using sys.argv is the most basic approach to read CLI arguments.