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Now you can: Use the zip() function in both Python 3 and Python 2. Loop over multiple iterables and perform different actions on their items in parallel. Create and update dictionaries on the fly by zipping two input iterables together.
Unless your generator is infinite, you can iterate through it one time only. Once all values have been evaluated, iteration will stop and the for loop will exit. If you used next() , then instead you'll get an explicit StopIteration exception.
It is fairly simple to create a generator in Python. It is as easy as defining a normal function, but with a yield statement instead of a return statement. If a function contains at least one yield statement (it may contain other yield or return statements), it becomes a generator function.
A generator expression is an expression that returns a generator object. Basically, a generator function is a function that contains a yield statement and returns a generator object.
itertools.chain() should do it.
It takes a list of iterables and yields from each one by one
def chain(*iterables):
for it in iterables:
for element in it:
yield element
Usage example:
from itertools import chain
generator = chain('ABC', 'DEF')
for item in generator:
print(item)
Output:
A
B
C
D
E
F
A example of code:
from itertools import chain
def generator1():
for item in 'abcdef':
yield item
def generator2():
for item in '123456':
yield item
generator3 = chain(generator1(), generator2())
for item in generator3:
print item
In Python (3.5 or greater) you can do:
def concat(a, b):
yield from a
yield from b
from itertools import chain
x = iter([1,2,3]) #Create Generator Object (listiterator)
y = iter([3,4,5]) #another one
result = chain(x, y) #Chained x and y
With itertools.chain.from_iterable you can do things like:
def genny(start):
for x in range(start, start+3):
yield x
y = [1, 2]
ab = [o for o in itertools.chain.from_iterable(genny(x) for x in y)]
print(ab)
Here it is using a generator expression with nested fors:
a = range(3)
b = range(5)
ab = (i for it in (a, b) for i in it)
assert list(ab) == [0, 1, 2, 0, 1, 2, 3, 4]
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