[python] SyntaxError: non-default argument follows default argument

from os import system
def a(len1,hgt=len1,til,col=0):
    system('mode con cols='+len1,'lines='+hgt)
    system('title',til)
    system('color',col)

a(64,25,"hi","0b")
input()

When I run this, it rejects "def a(..." and highlights "(" in red. I have no clue why.

You can't have a non-keyword argument after a keyword argument.

Make sure you re-arrange your function arguments like so:

def a(len1,til,hgt=len1,col=0):
    system('mode con cols='+len1,'lines='+hgt)
    system('title',til)
    system('color',col)

a(64,"hi",25,"0b")

As the error message says, non-default argument til should not follow default argument hgt.

Changing order of parameters (function call also be adjusted accordingly) or making hgt non-default parameter will solve your problem.

def a(len1, hgt=len1, til, col=0):

->

def a(len1, hgt, til, col=0):

UPDATE

Another issue that is hidden by the SyntaxError.

os.system accepts only one string parameter.

def a(len1, hgt, til, col=0):
    system('mode con cols=%s lines=%s' % (len1, hgt))
    system('title %s' % til)
    system('color %s' % col)