I am new to python and I want to append two lists in the following way:
list1=[2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2008, 2013, 2014]
list2=['Bahamas, The', 'Bahamas, The', 'Bahamas, The', 'Bahamas, The', 'Bahamas, The', 'Bahamas, The', 'Bahamas, The', 'Bahamas, The', 'Bahamas, The', 'Bahrain', 'Guyana', 'Guyana']
length of list 1 and list 2 are always equal in any condition.
I want the output to be :
2006: [’Bahamas, The’]
2007: [’Bahamas, The’]
2008: [’Bahamas, The’, ’Bahrain’]
2009: [’Bahamas, The’]
2010: [’Bahamas, The’]
2011: [’Bahamas, The’]
2012: [’Bahamas, The’]
2013: [’Bahamas, The’, ’Guyana’]
2014: [’Bahamas, The’, ’Guyana’]
I think the data structure you're looking for is a dictionary.
Using this data structure, we can do the following.
from collections import defaultdict
Create a new defaultdict and pass it list.
d = defaultdict(list)
Next we need to zip the two lists.
This can be done with:
zip(list1, list2)
If you're using Python 2, this will return a list (great, easy). However, if you're using Python 3, this produces a generator (see here). So, if you're using Python 3 (like me) to see what this thing looks like you can convert the generator to a list as follows:
list(zip(list1, list2))
Which is something like this:
[(2006, 'Bahamas, The'), (2007, 'Bahamas, The'), (2008, 'Bahamas, The')...]
Now all we have to do is iterate through this object as follows:
for k, v in zip(list1, list2):
d[k].append(v)
So, all together:
from collections import defaultdict
d = defaultdict(list)
for k, v in zip(list1, list2):
d[k].append(v)
To see the result you can use:
for k, v in d.items(): # iteritems if Python 2
print(k, v)
This yields:
2006 ['Bahamas, The']
2007 ['Bahamas, The']
2008 ['Bahamas, The', 'Bahrain']
2009 ['Bahamas, The']
2010 ['Bahamas, The']
2011 ['Bahamas, The']
2012 ['Bahamas, The']
2013 ['Bahamas, The', 'Guyana']
2014 ['Bahamas, The', 'Guyana']
FYI.
If you'd really like a list, and not a dictionary, you can use:
list(d.items()) # Python 3
list(d.iteritems()) # Python 2