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.")