After reading this Python Dictionaries topic, you will understand how to create the dictionary, and you will know how to accessing Items, changing Items and use Python dictionary built-in methods.
A Dictionary is a variable that collects same or different type of elements(items) does not exist in a sequence. The elements of the dictionary cannot repeat and dictionary elements support key. Unlike an index which supports integer only, a key can support integer or string.
How to create Dictionary in python?
The dictionary items should be written within the round brackets (i.e. ()) and each item separated by a comma (,).
Example:
Program (1): To demonstrate how to create and display dictionary in Python.
# storing sports items cricket, football and hockey in the dictionary x={1:'cricket', 2:'football', 3:'hockey'} # print a dictionary print(x)
Output(1)
{1: 'cricket', 2: 'football', 3: 'hockey'}
Accessing Items from Dictionary
Example:
Program (1): To demonstrate how to create dictionary and access dictionary items in Python.
# storing sports items cricket, football and hockey in the dictionary x={1:'cricket', 2:'football', 3:'hockey'} print(x[1]) print(x[2])
Output(1)
cricket football
Explanation: for Program(1) and Output(1)
- statement print(x[1]) gives output cricket describe the first item of dictionary, associated with key integer value 1.
- statement print(x[2]) gives output 3 describe the second item of dictionary, associated with key integer value 2.
Changing Items from Dictionary
Example:
Program (1): To show how changing dictionary items in Python.
# storing sports items cricket, football and hockey in the dictionary x={1:'cricket', 2:'football', 3:'hockey'} # print a dictionary print(x) #change cricket as item to basketball x[1]= 'basketball' # print dictionary with changed items print(x)
Output(1)
{1: 'cricket', 2: 'football', 3: 'hockey'} {1: 'basketball', 2: 'football', 3: 'hockey'}
Adding item to the Dictionary:
We can insert the item at the particular position defined by new key in the dictionary.
Example:
Program (1): To show how to add an item at the particular position in the dictionary.
# storing sports items cricket, football and hockey in the dictionary x={1:'cricket', 2:'football', 3:'hockey'} # insert item into the dictionary. x[4]='basketball' # print dictionary print(x)
Output(1)
{1: 'cricket', 2: 'football', 3: 'hockey', 4: 'basketball'}
Using loop over the Dictionary
Using a loop in the dictionary means we move through the dictionary and visit each item of the dictionary.
Example:
Program (1): To show how to use a loop on the dictionary to access dictionary items in Python.
# storing sports items cricket, football and hockey in the dictionary x={1:'cricket', 2:'football', 3:'hockey'} # print a dictionary print(x) # use for loop in order to print each item of the dictionary for i in x: print(x[i])
Output(1)
{1: 'cricket', 2: 'football', 3: 'hockey'} cricket football hockey
Dictionary handling built-in methods
Some of commonly used dictionary handling methods like len(), clear(), pop() and clear().
len() : This method gives the total number of items in the dictionary.
# storing sports items cricket, football and hockey in the dictionary x={1:'cricket', 2:'football', 3:'hockey'} # using len() method to calculate to the total number of items in the dictionary. print(len(x))
Output(1)
3
del() : This method remove an item from the dictionary.
# storing sports items cricket, football and hockey in the dictionary x={1:'cricket', 2:'football', 3:'hockey'} # using del() method to remove cricket as item from the dictionary del(x[1]) # print dictionary print(x)
Output(1)
{2: 'football', 3: 'hockey'}
pop() : This method also removes an item from the particular position defined by a key of the dictionary.
# storing sports items cricket, football and hockey in the dictionary x={1:'cricket', 2:'football', 3:'hockey'} # using pop() item from the dictionary. x.pop (2) # print dictionary print(x)
Output(1)
{1: 'cricket', 3: 'hockey'}
clear() : This method remove all items from the dictionary.
# storing sports items cricket, football and hockey in the dictionary x={1:'cricket', 2:'football', 3:'hockey'} # using clear() method to remove all items x.clear() # print dictionary print(x)
Output(1)
{}