Python 3.x Dictionaries and Sets Cheatsheet

Python 3.x - Dictionaries and Sets
Cheatsheet

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Commonly used Dictionaries Manipulation Commands
● Declare an empty dictionary: d = dict() or d = {}
● Create a dictionary with pre-existing key-value pairs: d = {<key1>: <value1>, <key2>:
<value2>, <key3>: <value3>, ….}
● Computing number of entries in dictionary: len(d)
● Add new key-value pair to dictionary: d[<key>] = value
● Iterate over key-value pairs:
for <key>, <value> in d.items():
print("Key:", <key>, " Value:", <value>)
● Iterate over keys:
for <key> in d.keys():
print("Key:", <key>)
● Iterate over values:
for <value> in d.values():
print("Value:", <value>)
● Remove an item from dictionary: del d[<key>]
● Remove an item from dictionary and return that to a variable using its key: var = d.pop(<key>)
● Remove an item from dictionary and return it as a tuple using key-value pair of an entry in it: var =
d.popitem(<key>, <value>)
● Alternative access to a key-value pair. This method will also not throw KeyError exception instead a
default which can be set(second parameter of the method) by the user or throws None:
d.get(<key>, "No match found!")
● Create dictionary from sequence of keys: d.fromkeys(<keys(can be in the form of list,
tuple or set)>, <value>)
● Update dictionary - either you can change existing entry in the dictionary or add a new entry to the
dictionary: d.update({'existing key': <new_value>, 'existing key2':
<new_value2>, 'new key': <new_value>....})
● Create dictionary comprehension from arbitrary key and value expressions: {x: x**2 for x in
(2, 4, 6, <any other numbers>....)}
● Return a shallow copy of dictionary to a variable: var = d.copy()
● Clear all entries from the dictionary: d.clear()
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Commonly used Sets Manipulation Commands
Note: Sets are used to remove duplicate items. It doesn't care about the order of the elements inside it as it
always displays its items randomly.
● Declaration of a new set: s = set()
● Adding a new element to the set. There is no effect the element is already present in the set:
s.add(<Element to be added>)
● Finding elements which are common between two or more sets: s.intersection(<set1 to be
compared, <set2 to be compared>....)
● Finding elements which are not common between two or more sets: s.difference(<set1 to be
compared, <set2 to be compared>....)
● Combining two or more set: s.union(<set1 to be combined>, <set2 to be
combined>....)
● Remove all elements of another set(s) from a set: s.difference_update(<another set1>,
<another set2>....)
● Update set with the intersection itself and another set(s): s.intersection_update(<another
set1>, <another set2>....)
● Update a set with the union of itself and another set(s): s.update(<another set1>, <another
set2>....)
● Clear all the elements from a set: s.clear()
● Return a shallow copy of a set: s.copy()
● Return elements between two sets(not more than that) that are not common among each other. This is
known as symmetric difference between two sets: s.symmetric_difference(<another set>)
● Returns True if two sets are having intersection None: s.isdisjoint(<another set>)
● Returns True if another set contains this set: s.issubset(<another set>)
● Returns True if a set contains another set: s.issuperset(<another set>)
● Update a set with its symmetric difference of another set:
s.symmetric_difference_update(<another set>)
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Python 3.x Dictionaries and Sets Cheatsheet

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Python 3.x Dictionaries and Sets Cheatsheet