This chapter explores lists and dictionaries, two essential data structures in programming, explaining their functions and importance for data manipulation.
Working with Lists and Dictionaries - Quick Look Revision Guide
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Key Points
Lists are mutable sequences.
In Python, lists can be modified after creation, allowing changes in contents as needed.
Access list elements using indices.
Elements can be accessed using indices starting from 0. Negative indices refer to elements from the end.
List concatenation with '+' operator.
Combine lists using the '+' operator; original lists remain unchanged.
List repetition with '*' operator.
Repeat the contents of a list using the '*' operator; duplicates are created.
Membership operator 'in'.
Check if an element exists in a list using 'in', returning True or False.
List slicing creates sublists.
Use slicing notation to create sublists by specifying start and end indices.
Common list methods: append, remove.
Use 'append()' to add elements, and 'remove()' to delete specific values from a list.
Traverse lists using loops.
Iterate through a list with 'for' or 'while' loops, accessing and manipulating elements.
Dictionaries are key-value pairs.
Dictionaries store data as pairs where keys are unique and map to their corresponding values.
Access dictionary values with keys.
Retrieve values by referencing their unique keys; use 'get()' to avoid errors on missing keys.
Dictionary methods: keys(), values().
Use 'keys()' to get a list of keys, and 'values()' to retrieve all values in the dictionary.
Dictionaries are mutable.
We can change contents by adding new key-value pairs or updating existing ones in dictionaries.
Check existence in dictionaries.
Use 'in' to test if a key exists; 'not in' checks for the absence of a key.
Length of lists and dictionaries.
Use 'len()' to find the number of items in lists or key-value pairs in dictionaries.
Sorting lists with 'sort()' and 'sorted()'.
'sort()' modifies the original list, while 'sorted()' returns a new sorted list.
Error handling in lists.
Accessing out of range indices leads to IndexError; handle exceptions for robust code.
Pop and delete methods in lists.
'pop()' removes an element at a specified index; 'del' can remove elements or entire lists.
Dictionary update with 'update()'.
Merge another dictionary into the current one using the 'update()' method.
Clear dictionary with 'clear()'.
Remove all key-value pairs from a dictionary using the 'clear()' method.
Real-world applications of lists and dictionaries.
Used for data manipulation, storing user information, or maintaining collections of items.
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