This tutorial is about Python dictionary which is data-structure representing key-value pairs, you can also call it a HashMap.
One of the very common use of hashmap is finding frequency of characters in a string
One of the very common use of hashmap is finding frequency of characters in a string
Basically a dictionary is like a list but instead of integer index it can be of any type
to define a dictionary we use a key-value pair with a colon between them.
in the example below, "one" maps to 1
also note that a dictionary is un-ordered, it may not show the items in the order it was defined.
>>> my_dict = {"one":1,"two":2,"three":3} >>> my_dict {'three': 3, 'two': 2, 'one': 1} #un-ordered items >>> my_dict["one"] #we are using a string as an index 1 >>> my_dict["two"] 2 >>> my_dict["three"] 3 >>>
we can also create an empty dictionary and add items to it later.
>>> my_dict = {} >>> my_dict["one"] = 1 >>> my_dict["two"] = 2 >>> my_dict["three"] = 3 >>> my_dict {'three': 3, 'two': 2, 'one': 1} >>> my_dict["one"] 1 >>> my_dict["two"] 2 >>> my_dict["three"] 3 >>>
Take user input in a Dictionary
n=int(input("Enter max items for the dictionary")) for i in range(n): key=input("Enter the key: ") value=input("Enter the value: ") dict1[key]=value
Looping Through a Dictionary
>>> for key in my_dict: ... print(key, my_dict[key]) ... ('three', 3) ('two', 2) ('one', 1) >>>
Check if a particular key is present in the dictionary
>>> 'one' in my_dict True >>> 'blabla' in my_dict False >>>
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