Page 424 - Computer Science V2.0 Class 11

14.5 Dictionary Methods

Python provides several methods for manipulating dictionaries. Unlike strings and tuples, a dictionary is a mutable
object. To invoke a method associated with a dictionary object, the dict object is followed by a dot, followed by the
name of the method, followed by a pair of parentheses that encloses the arguments (if any) required for invoking the
method. Using a dictionary object myDict, we describe some methods that apply to the dictionaries
● myDict.keys(): The method keys() returns a dict_keys object comprising all the keys included in
the dictionary. We can iterate over the keys in the dict_keys object and also check for membership of a key.
However, dict_keys does not support indexing.
Example:

>>> subjects
{'Sanskrit': 78, 'English': 185, 'Maths': 88, 'Hindi': 90}
>>> subjects.keys()
dict_keys(['Sanskrit', 'English', 'Maths', 'Hindi'])
>>> 'English' in subjects.keys()
True
>>> for subject in subjects.keys():
... print(subject, end = ' ')
...
...
Sanskrit English Maths Hindi
>>> subjects.keys()[0]
Traceback (most recent call last):
File "<pyshell#38>", line 1, in <module>
subjects.keys()[0]
TypeError: 'dict_keys' object is not subscriptable

Consider the dictionary, myDict.

>>> myDict = { 'b':'beta', 'g':'gamma', 'a':'alpha' }
Display all the keys of myDict.

● myDict.values(): The method values() returns a dict_values object comprising all the values
included in the dictionary. We can iterate over the values in the dict_values object and also, check for
membership of a value in a dict_values. However, dict_values does not support indexing.
Example
>>> 78 in subjects.values()
True
>>> for subjectCode in subjects.values():
... print(subjectCode, end=' ')
...
...
78 185 88 90
● myDict.items(): The method items() returns a dict_items object comprising the set of items
included in the dictionary. We can check for membership of an item in a dict_items and iterate over the items
in the dict_items object. However, dict_items does not support indexing.
Example:

>>> subjects = {'Sanskrit': 78, 'English': 185, 'Maths': 88, 'Hindi': 90}
>>> ('English', 185) in subjects.items()
True
for subject in subjects.items():
... print(subject, end=' ')

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