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Given a list, write a Python program to convert the given list to dictionary such that all the odd elements have the key, and even number elements
have the value. Since python dictionary is unordered, the output can be in any order.
Examples:
Input : ['a', 1, 'b', 2, 'c', 3]
Output : {'a': 1, 'b': 2, 'c': 3}
Input : ['Delhi', 71, 'Mumbai', 42]
Output : {'Delhi': 71, 'Mumbai': 42}
Method #1 : dict comprehension
To convert a list to dictionary, we can use list comprehension and make a key:value pair of consecutive elements. Finally, typecase the list to dict type.
Python3
def Convert[lst]:
res_dct =
{lst[i]: lst[i + 1] for i in range[0, len[lst], 2]}
return res_dct
lst = ['a', 1, 'b', 2, 'c', 3]
print[Convert[lst]]
Output
{'a': 1, 'b': 2, 'c': 3}
Method #2 : Using zip[] method
First create an iterator, and
initialize it to variable ‘it’. Then use zip method, to zip keys and values together. Finally typecast it to dict type.
Python3
def Convert[a]:
it = iter[a]
res_dct = dict[zip[it, it]]
return res_dct
lst = ['a', 1, 'b', 2, 'c', 3]
print[Convert[lst]]
Output
{'a': 1, 'b': 2, 'c': 3}
Till now, we have seen the ways to creating dictionary in multiple ways and different operations on the key and values in dictionary. Now, let’s see different ways of creating a dictionary of list.
Note that the restriction with keys in Python dictionary is only immutable data types can be used as
keys, which means we cannot use a dictionary of list as a key.
myDict = {[1, 2]: 'Geeks'}
print[myDict]
Output:
TypeError: unhashable type: 'list'
But the same can be done very wisely with values in dictionary. Let’s see all the different ways we can create a dictionary of Lists.
Method #1: Using subscript
myDict = {}
myDict["key1"] = [1, 2]
myDict["key2"] = ["Geeks", "For", "Geeks"]
print[myDict]
Output:
{'key2': ['Geeks', 'For', 'Geeks'], 'key1': [1, 2]}
Method #2: Adding nested list as value using append[] method.
Create a new list and we can simply append that list to the value.
myDict = {}
myDict["key1"] =
[1, 2]
lst = ['Geeks', 'For', 'Geeks']
myDict["key1"].append[lst]
print[myDict]
Output:
{'key1': [1, 2, ['Geeks', 'For', 'Geeks']]}
Method #3: Using setdefault[] method
Iterate the list and keep appending the elements till given range using setdefault[] method.
myDict = dict[]
valList =
['1', '2', '3']
for val in valList:
for ele in range[int[val], int[val] + 2]:
myDict.setdefault[ele, []].append[val]
print[myDict]
Output:
{1: ['1'], 2: ['1', '2'], 3: ['2', '3'], 4: ['3']}
Method #4: Using list comprehension
d =
dict[[val, range[int[val], int[val] + 2]]
for val in ['1', '2', '3']]
print[d]
Output:
{'1': [1, 2], '3': [3, 4], '2': [2, 3]}
Method #5: Using defaultdict
Note that the same thing can also be done with simple dictionary but using defaultdict is more efficient for such
cases.
from collections import defaultdict
lst = [['Geeks', 1], ['For', 2], ['Geeks', 3]]
orDict = defaultdict[list]
for key, val in lst:
orDict[key].append[val]
print[orDict]
Output:
defaultdict[, {'For': [2], 'Geeks': [1, 3]}]Note that there are only two key:value pairs in output dictionary but the input list contains three tuples. The
first element[i.e. key] is same for first and third tuple and two keys can never be same.
Method #6: Using Json
import json
lst = [['Geeks', 1], ['For', 2], ['Geeks', 3]]
dict = {}
hash = json.dumps[lst]
dict[hash] = "converted"
print[dict]
Output:
{'[["Geeks", 1], ["For", 2], ["Geeks", 3]]': 'converted'}