In Python what type of object does *zip(list1, list2) return?
Possible Duplicate:
Python: Once and for all. What does the Star operator mean in Python?
x = [1, 2, 3]
y = [4, 5, 6]
zipped = zip(x, y)
list(zipped)
x2, y2 = zip(*zip(x, y))
x == list(x2) and y == list(y2)
What type of object does *zip(x, y) return? Why
res = *zip(x, y)
print(res)
doesn't work?
The asterisk "operator" in Python does not return an object; it's a syntactic construction meaning "call the function with the list given as arguments."
So:
x = [1, 2, 3]
f(*x)
is equivalent to:
f(1, 2, 3)
Blog entry on this (not mine): http://www.technovelty.org/code/python/asterisk.html
The * operator in python is commonly known as scatter, it is useful for scatter tuples or lists into a number of variables, and thus is commonly used for input arguments. http://en.wikibooks.org/wiki/Think_Python/Tuples
The double star ** does the same operation on a dictionary, and is very useful for named arguments!
*zip(x, y) does not return a type, the * is used to unpack arguments to a function, in your case again zip .
With x = [1, 2, 3] and y = [4, 5, 6] the result of zip(x, y) is [(1, 4), (2, 5), (3, 6)] .
This means that zip(*zip(x, y)) is the same as zip((1, 4), (2, 5), (3, 6)) and the result of that becomes [(1, 2, 3), (4, 5, 6)] .