CODEWITHSUNDEEP
pythonpython-turtle
AKENY
AKENY

Reputation: 1

How do i call a function that requires an argument on key press? Python

I am a beginner programmer, sorry if the answer is obvious. Any help is appreciated. I am currently using WIN.onkeypress() to call functions but my scroll_draw_col function requires the argument curr_draw_col. I know WIN.onkeypress() can't pass arguments to their function. How do I call the scroll_draw_col function with curr_draw_col as an argument on keypress ("f")?

def scroll_draw_col(curr_draw_col):
    curr_draw_col += 1


WIN.listen()
WIN.onkeypress(tri_fwd, 'Up')  # Unrelated
WIN.onkeypress(tri_bkw, 'Down')  # Unrelated

WIN.onkeypress(tri_left, 'Left')  # Unrelated
WIN.onkeypress(tri_right, 'Right')  # Unrelated

WIN.onkeypress(scroll_draw_col, 'f')  # <-----

while True:
    WIN.update()
    dra.goto(tri.xcor(), tri.ycor())  # Unrelated
    print(curr_draw_col)  # To see if curr_draw_col is being incremented by 1

Upvotes: 0

Views: 56

Answers (2)

jhylands
jhylands

Reputation: 1014

I'm sure Lecdi's answer is sufficient but I thought I might add a couple more methods. It looks like what you are trying to do with this function call is change some state, increment a variable. For this, there are two techniques I'd suggest. For your particular use case, I would suggest a class.

class DrawColTrack:
    def __init__(self):
        self.col = 0
    def increment(self):
        self.col+=1


draw_col_tracker = DrawColTrack()

WIN.listen()
WIN.onkeypress(tri_fwd, 'Up')  # Unrelated
WIN.onkeypress(tri_bkw, 'Down')  # Unrelated

WIN.onkeypress(tri_left, 'Left')  # Unrelated
WIN.onkeypress(tri_right, 'Right')  # Unrelated

WIN.onkeypress(draw_col_tracker.increment, 'f')  # <-----

while True:
    WIN.update()
    dra.goto(tri.xcor(), tri.ycor())  # Unrelated
    print(draw_col_tracker.col)  # To see if curr_draw_col is being incremented by 1

The other way which I think is worth mentioning on the topic of lambdas etc is to create a closure.

def gen_col_incrementer(starting_value):
    def _():
       starting_value+=1
       return starting_value
    return _
increment = gen_col_incrementer(0)
assert 1 == increment()

Upvotes: 1

Lecdi
Lecdi

Reputation: 2241

Simply use global and remove the argument altogether. However, for future reference, you can pass an argument to a function without running it by using lambda:

# What you should do
def scroll_draw_col():
    global curr_draw_col
    curr_draw_col += 1


WIN.listen()
WIN.onkeypress(tri_fwd, 'Up')  # Unrelated
WIN.onkeypress(tri_bkw, 'Down')  # Unrelated

WIN.onkeypress(tri_left, 'Left')  # Unrelated
WIN.onkeypress(tri_right, 'Right')  # Unrelated

WIN.onkeypress(scroll_draw_col, 'f')  # <-----

while True:
    WIN.update()
    dra.goto(tri.xcor(), tri.ycor())  # Unrelated
    print(curr_draw_col)  # To see if curr_draw_col is being incremented by 1 

# If you wanted to pass an argument on a key press
WIN.onkeypress(lambda: function_name(argument), 'f')

Upvotes: 1

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