100
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.

4

4 Answers 4

176

Let me clarify two points here:

  • Firstly non-default argument should not follow the default argument, it means you can't define (a='b', c) in function. The correct order of defining parameter in function are:
    • positional parameter or non-default parameter i.e (a, b, c)
    • keyword parameter or default parameter i.e (a='b', r='j')
    • keyword-only parameter i.e (*args)
    • var-keyword parameter i.e (**kwargs)
def example(a, b, c=None, r="w", d=[], *ae,  **ab):

(a,b) are positional parameter

(c=none) is optional parameter

(r="w") is keyword parameter

(d=[]) is list parameter

(*ae) is keyword-only

(*ab) is var-keyword parameter

so first re-arrange your parameters

  • now the second thing is you have to define len1 when you are doing hgt=len1 the len1 argument is not defined when default values are saved, Python computes and saves default values when you define the function len1 is not defined, does not exist when this happens (it exists only when the function is executed)

so second remove this "len1 = hgt" it's not allowed in python.

keep in mind the difference between argument and parameters.

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1 Comment

Don't use an empty list as a default value for a function parameter, it gets carried across runs. Use None instead.
20

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)

2 Comments

THANK YOU. One more thing, could you please give me a link to any youtube Python tutorial series THAT ISN'T OUT OF DATE? plz?
@AidanCodeX, I don't know about youtube Python tutorial. How about Python tutorial from python.org ?
15

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")

1 Comment

Best simple and helpful answer for me. I think Python should fix this.
0

Inside the function all the variables should be defined in the same format. While you have given default values to some variables.

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

It should be like

def(len1, hgt, til, col):

or

def(len1=value, hgt=value, til=value, col=value):

Comments

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