#!/usr/bin/env python
# coding: utf-8

# #zip
# 
# zip() makes an iterator that aggregates elements from each of the iterables.
# 
# Returns an iterator of tuples, where the i-th tuple contains the i-th element from each of the argument sequences or iterables. The iterator stops when the shortest input iterable is exhausted. With a single iterable argument, it returns an iterator of 1-tuples. With no arguments, it returns an empty iterator. 
# 
# zip() is equivalent to:
# 
#     def zip(*iterables):
#         # zip('ABCD', 'xy') --> Ax By
#         sentinel = object()
#         iterators = [iter(it) for it in iterables]
#         while iterators:
#             result = []
#             for it in iterators:
#                 elem = next(it, sentinel)
#                 if elem is sentinel:
#                     return
#                 result.append(elem)
#             yield tuple(result)
#         
# 
# zip() should only be used with unequal length inputs when you don’t care about trailing, unmatched values from the longer iterables. 
# 
# Lets see it in action in some examples:
# 
# ##Examples

# In[1]:


x = [1,2,3]
y = [4,5,6]

# Zip the lists together
zip(x,y)


# Note how tuples are returned. What if one iterable is longer than the other?

# In[2]:


x = [1,2,3]
y = [4,5,6,7,8]

# Zip the lists together
zip(x,y)


# Note how the zip is defined by the shortest iterable length. Its generally advised not to zip unequal length iterables unless your very sure you only need partial tuple pairings.
# 
# What happens if we try to zip together dictionaries?

# In[4]:


d1 = {'a':1,'b':2}
d2 = {'c':4,'d':5}

zip(d1,d2)


# This makes sense because simply iterating through the dictionaries will result in just the keys. We would have to call methods to mix keys and values:

# In[6]:


zip(d2,d1.itervalues())


# Great! Finally lets use zip a to switch the keys and values of the two dictionaries:

# In[7]:


def switcharoo(d1,d2):
    dout = {}
    
    for d1key,d2val in zip(d1,d2.itervalues()):
        dout[d1key] = d2val
    
    return dout


# In[8]:


switcharoo(d1,d2)


# Great! You can use zip to save a lot of typing in many situations! You should now have a good understanding of zip() and some possible use cases.