7.5.2. Accessing Items

In this section, we'll see how the items stored in a dictionary can be accessed.

Subscripting

We saw this syntax in the previous section too. We can pass the key to access value of in the square brackets similar to indexing lists.

CodeOutput

data = {
    'name': 'John',
    'age': 25,
}

print(data['age'])

25

In case the key provided does not exist, a KeyError is raised.

CodeOutput

data = {
    'name': 'John',
    'age': 25,
}

print(data['gender'])

Traceback (most recent call last):
  File "C:\XGuides\python\test.py", line 6, in <module>
    print(data['gender'])
          ~~~~^^^^^^^^^^
KeyError: 'gender'

dict.get() Method

dict.get() method can be used to access the value corresponding to a key too.

CodeOutput

data = {
    'name': 'John',
    'age': 25,
}

print(data.get('name'))

John

There's one difference in this method compared to the previous approach, if the key accessed does not exist, it returns None instead of raising a KeyError.

CodeOutput

data = {
    'name': 'John',
    'age': 25,
}

print(data.get('gender'))

None

Since gender didn't exist, None was returned. Alternatively, a default value could be provided as second parameter which is returned if key does not exist:

CodeOutput

data = {
    'name': 'John',
    'age': 25,
}

print(data.get('name', 'No name'))
print(data.get('gender', 'male'))

John
male

Since name key existed, its value was returned and default No name was ignored. In case of gender, the key didn't exist so default value was returned instead.

Accessing keys and values

A dictionary provides three methods to access its data:

dict.keys()

dict.keys() method returns an iterable that contains the dictionary keys.

CodeOutput

data = {
    'name': 'John',
    'age': 25,
}

print(data.keys())

dict_keys(['name', 'age'])

dict.values()

Similarly, dict.values() returns an iterable of values stored in the dictionary.

CodeOutput

data = {
    'name': 'John',
    'age': 25,
}

print(data.values())

dict_values(['John', 25])

dict.items()

dict.items() returns an iterable that has tuples representing key-value pairs where each tuple has two elements: key and value.

CodeOutput

data = {
    'name': 'John',
    'age': 25,
}

print(data.items())

dict_items([('name', 'John'), ('age', 25)])

Note

Do not confuse the returned values of each of these methods with ordinary lists. These methods return a special iterable.

It can be indexed and iterated over but cannot be modified.

Iterating over a dictionary

We can iterate over the items of a dictionary using a for loop and dict.items() method.

CodeOutput

data = {
    'name': 'John',
    'age': 25,
}

for key, value in data.items():
    print(f'{key} in data corresponds to {value}')

name in data corresponds to John
age in data corresponds to 25

As we saw earlier in this section, dict.items() returns an iterable of key-value tuples, we are simply looping through those tuples and unpacking the tuple values into key and value variables.

Note

Simply iterating over a dictionary without calling the dict.items() method loops through only the keys of the dictionary.

CodeOutput

data = {
    'name': 'John',
    'age': 25,
}

for x in data:
    print(x)

name
age