Python Global variable gives NameError

Question

My code:

def draw_lines(img, lines, color, thickness) :
    x_right = []
    y_right = []
    x_left = []
    y_left = []
    numItr = 1

    for line in lines :
        for x1,y1,x2,y2 in lines :
        global numItr
        numItr += 1

And this is error:

NameError: name 'numItr' is not defined

Please copy paste your code, also this says the variable was not defined before you use it — Seif, Feb 01 '17 at 11:46
what are parameter values you are passing to the function. can you post exact details?Let us know what are you trying to achieve with this code. — Shivkumar kondi, Feb 01 '17 at 12:26

Jacques de Hooge · Accepted Answer · 2017-02-01T13:09:29.353

No need to use global or nonlocal here, just:

def draw_lines(img, lines, color, thickness) :
    x_right = []
    y_right = []
    x_left = []
    y_left = []
    numItr = 1

    for line in lines :
        for x1,y1,x2,y2 in lines :
            numItr += 1

You only need global if you want to write to a module level variable. And you only need nonlocal if you want to write to a variable that's local to a lexically enclosing function, e.g. the function in which you define your function.

Both cases don't apply to your code, you're just staying inside one function.

In your case the interpreter complains, while by using the word global you indicate that there is a module level variable called numItr, which there isn't.

score 0 · Answer 2 · edited May 23 '17 at 11:45

0

Perhaps your problem is that numItr not declared before draw_lines function. look at this https://stackoverflow.com/a/423596/6876911

edited May 23 '17 at 11:45

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answered Feb 01 '17 at 12:35

sahama

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Python Global variable gives NameError

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