Python for in loop to generate dictionary
I came across this snippet of code, I understand it's a Cartesian product but if someone can break up this line for me [s+t for s in a for t in b] from the following code along with docs link for this kind of syntax.
Apparently this for in syntax with s+t ??? is foreign for me and I'm new to python as well. Appreciate docs link so I can understand more about this syntax since there are other variations of for in loops that I'm trying to understand.
rows = 'ABCDEFGHI'
cols = '123456789'
def cross(a, b):
return [s+t for s in a for t in b]
def main():
print(cross(rows, cols))
if __name__ == "__main__": main()
This is a shorthand syntax known as a list comprehension. See section 5.1.4 of the docs: https://docs.python.org/2/tutorial/datastructures.html
The line is exactly equivalent to this:
lst = []
for s in a:
for t in b:
lst.append(s+t)
return lst
It just finds the sums of every pair of an element in a and an element in b .
It can be broken down into:
lst = []
for s in A:
for t in b:
lst.append(s+t)
return lst
Hope this helps!
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