Add list to dictionary Python

In this article we will discuss different ways to convert a single or multiple lists to dictionary in Python.

Following conversions from list to dictionary will be covered here,

• Convert a List to Dictionary with same values
• Convert List items as keys in dictionary with enumerated value
• Convert two lists to dictionary
• Convert a list of tuples to dictionary

Convert a List to Dictionary with same values

Suppose we have a list of strings i.e.

# List of strings listOfStr = ["hello", "at" , "test" , "this" , "here" , "now" ]
Now we want to create a dictionary with all elements in this list as keys. For each key value will be same i.e. 5.Lets see how to do that i.e.

Using dictionary comprehension

''' Converting a list to dictionary with list elements as keys in dictionary All keys will have same value ''' dictOfWords = { i : 5 for i in listOfStr }
Dictionary contents will be,
hello :: 5 here :: 5 this :: 5 test :: 5 at :: 5 now :: 5
Using dict.fromKeys[]
''' Converting a list to dictionary with list elements as keys in dictionary using dict.fromkeys[] ''' dictOfWords = dict.fromkeys[listOfStr , 1]
dict.fromKeys[] accepts a list and default value. It returns a dictionary with items in list as keys. All dictionary items will have same value, that was passed in fromkeys[].

If no default value was passed in fromKeys[] then default value for keys in dictionary will be None.

Convert List items as keys in dictionary with enumerated value

Suppose we have a list of strings i.e.

# List of strings listOfStr = ["hello", "at" , "test" , "this" , "here" , "now" ]
Lets create a dictionary from this list with list elements as keys and values as integers from 0 to n-1 [n is size of list] i.e.
''' Converting a list to dictionary with list elements as values in dictionary and keys are enumerated index starting from 0 i.e. index position of element in list ''' dictOfWords = { i : listOfStr[i] for i in range[0, len[listOfStr] ] }
Dictionary contents will be,
0 :: hello 1 :: at 2 :: test 3 :: this 4 :: here 5 :: now

Convert two lists to a dictionary

Suppose we have two lists i.e.

# List of strings listOfStr = ["hello", "at" , "test" , "this" , "here" , "now" ] # List of ints listOfInt = [56, 23, 43, 97, 43, 102]
Lets create a dictionary with elements of listOfStr as keys and elements of listOfInt as values using zip[] i.e
# Create a zip object from two lists zipbObj = zip[listOfStr, listOfInt] # Create a dictionary from zip object dictOfWords = dict[zipbObj]
Zip[] accepts a number of iterable objects and returns a list of tuples. Each entry in tuple contains an element from each iterable object.
We have passed two lists objects in zip[] , so it will return a list of tuples, where each tuple contains an entry from both the lists.Then we created a dictionary object from this list of tuples.

Dictionary contents are,

Dictionary from two Lists hello :: 56 here :: 43 this :: 97 test :: 43 at :: 23 now :: 102

• If length of keys list is less than list of values then remaining elements in value list will be skipped.

Convert a list of tuples to dictionary

Suppose we have a list of tuples with two columns in each entry i.e.

# List of tuples listofTuples = [["Riti" , 11], ["Aadi" , 12], ["Sam" , 13],["John" , 22],["Lucy" , 90]]
We can directly pass this list of tuples to dictionary constructor i.e
# Convert a list of tuple to dictionary studentsDict = dict[listofTuples]
Entries in first column will become the key and entries in second column will the values in the new dictionary.Contents of dictionary will be,
Dictionary from List of Tuples John :: 22 Lucy :: 90 Riti :: 11 Aadi :: 12 Sam :: 13

Python Dictionary Tutorial - Series:

1. What is a Dictionary in Python & why do we need it?
2. Creating Dictionaries in Python
3. Iterating over dictionaries
4. Check if a key exists in dictionary
5. Check if a value exists in dictionary
6. Get all the keys in Dictionary
7. Get all the Values in a Dictionary
8. Remove a key from Dictionary
9. Add key/value pairs in Dictionary
10. Find keys by value in Dictionary
11. Filter a dictionary by conditions
12. Print dictionary line by line
13. Convert a list to dictionary
14. Sort a Dictionary by key
15. Sort a dictionary by value in descending or ascending order
16. Dictionary: Shallow vs Deep Copy
17. Remove keys while Iterating
18. Get all keys with maximum value
19. Merge two or more dictionaries in python

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Complete example is as follows,

''' Display contents of dictionary with each key/value pair in seperate line ''' def displatDict[text, dictOfElements] : print["*************"] print[text] for key , value in dictOfElements.items[]: print[key, " :: ", value] def main[]: # List of strings listOfStr = ["hello", "at" , "test" , "this" , "here" , "now" ] ''' Converting a list to dictionary with list elements as keys in dictionary All keys will have same value ''' dictOfWords = { i : 5 for i in listOfStr } displatDict["Dictionary with same value " , dictOfWords] ''' Converting a list to dictionary with list elements as keys in dictionary using dict.fromkeys[] ''' dictOfWords = dict.fromkeys[listOfStr , 1] displatDict["Dictionary with given default value " , dictOfWords] dictOfWords = dict.fromkeys[listOfStr] displatDict["Dictionary with same default value None " , dictOfWords] ''' Converting a list to dictionary with list elements as values in dictionary and keys are enumerated index starting from 0 i.e. index position of element in list ''' dictOfWords = { i : listOfStr[i] for i in range[0, len[listOfStr] ] } displatDict["Dictionary with enumerated keys" , dictOfWords] ''' Converting multiple lists to dictionary using zip list1 will be used as keys and list2 as values ''' # List of strings listOfStr = ["hello", "at" , "test" , "this" , "here" , "now" ] # List of ints listOfInt = [56, 23, 43, 97, 43, 102] # Create a zip object from two lists zipbObj = zip[listOfStr, listOfInt] # Create a dictionary from zip object dictOfWords = dict[zipbObj] displatDict["Dictionary from two Lists " , dictOfWords] ''' If list of keys is greater than list of values then extra keys will be skipped ''' # List of strings listOfStr = ["hello", "at" , "test" , "this" , "here" , "now" ] # List of ints listOfInt = [56, 23, 43, 97, 43] zipbObj = zip[listOfStr, listOfInt] dictOfWords = dict[zipbObj] displatDict["Dictionary from two Lists " , dictOfWords] ''' Convert a list of tuples to Dictionary ''' # List of tuples listofTuples = [["Riti" , 11], ["Aadi" , 12], ["Sam" , 13],["John" , 22],["Lucy" , 90]] # Convert a list of tuple to dictionary studentsDict = dict[listofTuples] displatDict["Dictionary from List of Tuples" , studentsDict] if __name__ == '__main__': main[]
Output
************* Dictionary with same value now :: 5 here :: 5 test :: 5 at :: 5 this :: 5 hello :: 5 ************* Dictionary with given default value now :: 1 here :: 1 test :: 1 at :: 1 this :: 1 hello :: 1 ************* Dictionary with same default value None now :: None here :: None test :: None at :: None this :: None hello :: None ************* Dictionary with enumerated keys 0 :: hello 1 :: at 2 :: test 3 :: this 4 :: here 5 :: now ************* Dictionary from two Lists now :: 102 here :: 43 test :: 43 at :: 23 this :: 97 hello :: 56 ************* Dictionary from two Lists test :: 43 at :: 23 this :: 97 hello :: 56 here :: 43 ************* Dictionary from List of Tuples John :: 22 Lucy :: 90 Riti :: 11 Aadi :: 12 Sam :: 13