How to map one list to another in python? [duplicate]

Answer 1

Use a set to only count each item once, use the list method count to count them, store them in a dict with the item as key and the occurrence is value.

l=["a","a","b","c","c","c"]
d={}

for i in set(l):
    d[i] = l.count(i)

print d

Output:

{'a': 2, 'c': 3, 'b': 1}

Answer 2

>>> x=['a','a','b','c','c','c']
>>> map(x.count,x)
[2, 2, 1, 3, 3, 3]
>>> dict(zip(x,map(x.count,x)))
{'a': 2, 'c': 3, 'b': 1}
>>>

Answer 3

Second one could be just

dict(zip(['a','a','b','c','c','c'], [2, 2, 1, 3, 3, 3]))

Answer 4

For the first one:

l = ['a','a','b','c','c','c']

map(l.count,l)

Answer 5

On Python ≥2.7 or ≥3.1, we have a built-in data structure collections.Counter to tally a list

>>> l = ['a','a','b','c','c','c']
>>> Counter(l)
Counter({'c': 3, 'a': 2, 'b': 1})

It is easy to build [2, 2, 1, 3, 3, 3] afterwards.

>>> c = _
>>> [c[i] for i in l]   # or map(c.__getitem__, l)
[2, 2, 1, 3, 3, 3]

Answer 6

This coding should give the result:

from collections import defaultdict

myDict = defaultdict(int)

for x in mylist:
  myDict[x] += 1

Of course if you want the list inbetween result, just get the values from the dict (mydict.values()).