Python Dictionary And It's Functions
A dictionary in Python is an unordered collection of key-value pairs, where each key is unique and can be used to retrieve its corresponding value. Dictionaries are defined using curly braces ({}
) and can be initialized in the following way:
Create A Dictionary Using this Syntax :
d = {'key1': 'value1', 'key2': 'value2', ...}
Here are some of the most commonly used methods and operations with dictionaries in Python:
-
len(d)
: Returns the number of key-value pairs in the dictionary. -
d[key]
: Returns the value associated with thekey
in the dictionary. If the key is not found, it raises a KeyError. -
d.get(key, default)
: Returns the value associated with thekey
in the dictionary. If the key is not found, it returns thedefault
value. -
key in d
: ReturnsTrue
if thekey
is in the dictionary, andFalse
otherwise. -
d.keys()
: Returns a view object that displays a list of all the keys in the dictionary. -
d.values()
: Returns a view object that displays a list of all the values in the dictionary. -
d.items()
: Returns a view object that displays a list of all the key-value pairs in the dictionary. -
d.update(other_dictionary)
: Adds the key-value pairs fromother_dictionary
tod
. If the same key exists in both dictionaries, the value ind
will be updated with the value fromother_dictionary
. -
d.pop(key, default)
: Removes the key-value pair associated with thekey
in the dictionary and returns its value. If the key is not found, it returns thedefault
value. -
d.clear()
: Removes all key-value pairs from the dictionary.
Note: The view objects returned by keys()
, values()
, and items()
methods are dynamic, which means that they reflect any changes made to the dictionary.
Create And Access Dictionary
In this example dictionary is created using curly brackets.
a = {"python":2000, "java":5000, "C++": 3000, "html": 1000}
print(a) # {'python': 2000, 'java': 5000, 'C++': 3000, 'html': 1000}
print(a["java"]) # 5000
print(a["python"]) # 2000
print(a["C++"]) # 3000
Create Dictionary Using Dict() Function
dict()
function is used to create a dictionary. It takes multiples arguments that is shown in the Examples
Syntax
dict() # empty dictionary
dict(iterable) # iterable object which has key value pair
dict(**kwargs) # key value pair seperated by comma dict(one=1, two=2)
Example:
# create dictionary using dict() function
b = dict({"rahul":100, "sonam":200, "arjun":300})
print(b) # {'rahul': 100, 'sonam': 200, 'arjun': 300}
a = dict() # empty dictionary
print(a) # {}
b = dict(python= 220, java= 300,cpp=340)
print(b) # {'python': 220, 'java': 300, 'cpp': 340}
Dictionary Get() Function
get()
function return the value of specified key, if key does not exist it raise keyError .
a = {'python': 220, 'java': 300, 'cpp': 340}
print(a)
print(a.get("python")) #220
Dictionary Pop() Function
pop()
function remove the element from dictionary with specified keys and return or if key does not exist raise keyError.
a = {'python': 220, 'java': 300, 'cpp': 340}
print(a.pop("python")) #220
print(a) # {'java': 300, 'cpp': 340}
Dictionary Popitem() Function
popitem()
remove the last key-value pair as tuple from the dictionary .
a = {'python': 220, 'java': 300, 'cpp': 340}
print(a.popitem()) # ('cpp', 340)
print(a) # {'python': 220, 'java': 300}
Dictionary Setdefault() Function
setdefault()
return the value of specified key if not exist set the value as specified .
a = {'python': 220, 'java': 300, 'cpp': 340}
print(a.setdefault("php")) # None
print(a) # {'python': 220, 'java': 300, 'cpp': 340, 'php': None}
# setdefault with key and value
a.setdefault("php",0)
print(a) # {'python': 220, 'java': 300, 'cpp': 340, 'php': 0}
Dictionary Update() Function
update()
function update the dictionary with specified key-value pair.
a = {'python': 220, 'java': 300, 'cpp': 340}
a.update(php=3450)
print(a) # {'python': 220, 'java': 300, 'cpp': 340, 'php': 3450}
Dictionary Items() Function
items()
function return the all keys-values as list of tuples.
a = {'python': 220, 'java': 300, 'cpp': 340}
print(a.items()) # dict_items([('python', 220), ('java', 300), ('cpp', 340)])
Dictionary Keys() Function
keys()
function return the all keys from the dictionary as list.
a = {'python': 220, 'java': 300, 'cpp': 340}
print(a.keys()) # dict_keys(['python', 'java', 'cpp'])
Dictionary Values() Function
values()
function return the all value of all keys as list.
a = {'python': 220, 'java': 300, 'cpp': 340}
print(a.values()) # dict_values([220, 300, 340])