What does "[," mean in Python arguments?

Asked Dec 05 '17 at 05:52

Active Dec 05 '17 at 06:13

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What does "[, ]" mean in Python args? They can be seen in input arguments such as:

cv2.Canny(image, threshold1, threshold2[, edges[, apertureSize[, L2gradient]]])

or scikit-learn; (e.g sklearn.linear_model.LinearRegression):

fit(X, y[, sample_weight])  Fit linear model.

What does y[, sample_weight] actually mean? Does it mean something like the first dimension in the array?

y[:,sample_weight]

Update: Thanks for the answers, it means optional. But why are they nested though?

threshold2[, edges[, apertureSize[, L2gradient]]]

edited Dec 05 '17 at 06:05

asked Dec 05 '17 at 05:52

Stark

5

optional....... – anthony sottile Dec 05 '17 at 05:53
Taking y[:,sample_weight] as an example, y is definitely not optional, so it means that the y could be either in 1 or 2 dimensions? – Stark Dec 05 '17 at 05:57
Thanks @KenY-N, that didn't show up when I tried to search – Stark Dec 05 '17 at 05:59
yes `y` is not optional, but `sample_weight` is. You see, the arguments inside square brackets are optional. – GadaaDhaariGeek Dec 05 '17 at 05:59

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