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My mind just cannot visualize what zip is doing. I’ve written production code with zip and I’ve finished leetcode problems with zip. But every single time I nee

by teej 6y ago

My mind just cannot visualize what zip is doing. I’ve written production code with zip and I’ve finished leetcode problems with zip. But every single time I need a piece of paper to help me through it. I’m fine with most of the rest of Python’s functional-style iterable helpers. But something about zip just doesn’t work for me.

Groxx 6y ago
Zip is just "pair each x with each y". Literally: [1,2,3,4] [5,6,7,8] # go down each column, yielding these in order [1,5] [2,6] [3,7] [4,8] And then you drop ones with no pair. So zipping [1] and [2,3] makes just [1,2]. The same is true if you reverse the arguments, so [1,2] and [3] => [1,3] The example is sorta obtuse at a glance[1], but this: `zip(xs, xs[1:])` equates to this: [1,2,3,4] [2,3,4] # copy and drop the first element # outputs columns [1,2] [2,3] [3,4] So it's a one-liner to make a list of of each consecutive pair of items in a list. All `zip(x, x[1:])` do the same thing regardless of the ultimate use of such a construct. But yeah, I have seen some very confusing uses of zip before sitting and thinking for a bit. TBH I think much of it is just familiarity though - after seeing a million `for (i=0;i<thing.len();i++) { ... }` I can pattern-match and figure this out easily: for (i=0, l=thing.len(); i<l-1; i++) { list.push([thing[i], thing[i+1]]) } (though `i<l-1` ease may depend on font) but similarly-common functional idioms just don't slide into position as easily. Yet. [1]: I'm guessing it's the equivalent of finding the largest "gap" between a bunch of sizes of things.
floxy 6y ago
Think of a physical zipper, where the two sides with the teeth come together to interlock... xs = [1,2,3,4,5,6,... ys = [a,b,c,d,e,f,... [ (1,a), (2,b), (3,c), (4,d), (5,e), |6| |f| |7| |g| |8| |h| |9| |i| |0| |j| . . . . . . ] https://kezan.eu/wp-content/uploads/2016/05/Zipper_Thumb_1440.jpg https://kezan.eu/wp-content/uploads/2016/05/Zipper_Thumb_144...

by teej 6y ago

Groxx 6y ago

Zip is just "pair each x with each y". Literally: [1,2,3,4] [5,6,7,8] # go down each column, yielding these in order [1,5] [2,6] [3,7] [4,8] And then you drop ones with no pair. So zipping [1] and [2,3] makes just [1,2]. The same is true if you reverse the arguments, so [1,2] and [3] => [1,3] The example is sorta obtuse at a glance[1], but this: `zip(xs, xs[1:])` equates to this: [1,2,3,4] [2,3,4] # copy and drop the first element # outputs columns [1,2] [2,3] [3,4] So it's a one-liner to make a list of of each consecutive pair of items in a list. All `zip(x, x[1:])` do the same thing regardless of the ultimate use of such a construct. But yeah, I have seen some very confusing uses of zip before sitting and thinking for a bit. TBH I think much of it is just familiarity though - after seeing a million `for (i=0;i<thing.len();i++) { ... }` I can pattern-match and figure this out easily: for (i=0, l=thing.len(); i<l-1; i++) { list.push([thing[i], thing[i+1]]) } (though `i<l-1` ease may depend on font) but similarly-common functional idioms just don't slide into position as easily. Yet. [1]: I'm guessing it's the equivalent of finding the largest "gap" between a bunch of sizes of things.

floxy 6y ago

Think of a physical zipper, where the two sides with the teeth come together to interlock... xs = [1,2,3,4,5,6,... ys = [a,b,c,d,e,f,... [ (1,a), (2,b), (3,c), (4,d), (5,e), |6| |f| |7| |g| |8| |h| |9| |i| |0| |j| . . . . . . ] https://kezan.eu/wp-content/uploads/2016/05/Zipper_Thumb_1440.jpg https://kezan.eu/wp-content/uploads/2016/05/Zipper_Thumb_144...