Dictionaries and Sets Ali Taheri Sharif University of Technology - - PowerPoint PPT Presentation

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dictionaries and sets

Dictionaries and Sets Ali Taheri Sharif University of Technology - - PowerPoint PPT Presentation

Aug 23, 2023 134 likes •301 views

Fu Fundamentals of Pr Programming (Py Python) Dictionaries and Sets Ali Taheri Sharif University of Technology Spring 2019 Outline 1. Dictionary Basics 2. Dictionary Operations 3. Dictionary are Mutable 4. Iterating over Dictionary 5.

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Fu Fundamentals of Pr Programming (Py Python)

Dictionaries and Sets

Ali Taheri Sharif University of Technology

Spring 2019

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Outline

1. Dictionary Basics
2. Dictionary Operations
3. Dictionary are Mutable
4. Iterating over Dictionary
5. Dictionary Methods
6. Sparse Matrices
7. Sets

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ALI TAHERI - FUNDAMENTALS OF PROGRAMMING [PYTHON] Spring 2019

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Dictionary Basics

Dictionary is an unordered collection of key-value pairs

Each value can be accessed using its key
Keys can be any immutable object

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ALI TAHERI - FUNDAMENTALS OF PROGRAMMING [PYTHON] Spring 2019

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Dictionary Operations

Checking the existence of a key:

Using in operator

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ALI TAHERI - FUNDAMENTALS OF PROGRAMMING [PYTHON] Spring 2019

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List Operations

Deletion:

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ALI TAHERI - FUNDAMENTALS OF PROGRAMMING [PYTHON] Spring 2019

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Dictionaries are Mutable

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ALI TAHERI - FUNDAMENTALS OF PROGRAMMING [PYTHON] Spring 2019

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Output:

Iteration over Dictionaries

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Access built-in methods using dot operator:

Dictionary Methods

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ALI TAHERI - FUNDAMENTALS OF PROGRAMMING [PYTHON] Spring 2019

Method Meaning dict.keys() Returns a sequence of keys. dict.values() Returns a sequence of values. dict.items() Returns a sequence of tuples (key, value) representing the key-value pairs. dict.clear() Deletes all entries. dict.get(key, default) If dictionary has key returns its value;

therwise returns default.

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A sparse matrix is a matrix with lots of zeros!

Sparse Matrices

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ALI TAHERI - FUNDAMENTALS OF PROGRAMMING [PYTHON] Spring 2019

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Sets

Set is a collection of unique objects

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ALI TAHERI - FUNDAMENTALS OF PROGRAMMING [PYTHON] Spring 2019

x = set(["Postcard", "Radio", "Telegram"]) print(x) {'Telegram', 'Radio', 'Postcard'} y = {"Postcard","Radio","Telegram"} print(y) {'Telegram', 'Radio', 'Postcard'}

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Sets

Iteration

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ALI TAHERI - FUNDAMENTALS OF PROGRAMMING [PYTHON] Spring 2019

>>> num_set = set([0, 1, 2, 3, 4, 5]) >>> for n in num_set: print(n) 1 2 3 4 5 >>>

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Sets

Adding items

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ALI TAHERI - FUNDAMENTALS OF PROGRAMMING [PYTHON] Spring 2019

>>> color_set = set() >>> color_set.add("Red") >>> print(color_set) {'Red'} >>> color_set.update(["Blue", "Green"]) >>> print(color_set) {'Red', 'Blue', 'Green'} >>>

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Sets

Removing items

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ALI TAHERI - FUNDAMENTALS OF PROGRAMMING [PYTHON] Spring 2019

>>> num_set = set([0, 1, 2, 3, 4, 5]) >>> num_set.discard(3) >>> print(num_set) {0, 1, 2, 4, 5} >>>

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Sets

Intersection Union

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ALI TAHERI - FUNDAMENTALS OF PROGRAMMING [PYTHON] Spring 2019

>>> setx = set(["green", "blue"]) >>> sety = set(["blue", "yellow"]) >>> setz = setx & sety >>> print(setz) {'blue'} >>> setx = set(["green", "blue"]) >>> sety = set(["blue", "yellow"]) >>> seta = setx | sety >>> print (seta) {'yellow', 'blue', 'green'}

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Sets

Difference Symmetric Difference

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ALI TAHERI - FUNDAMENTALS OF PROGRAMMING [PYTHON] Spring 2019

>>> setx = set(["green", "blue"]) >>> sety = set(["blue", "yellow"]) >>> setc = setx ^ sety >>> print(setc) {'yellow', 'green'} >>> setx = set(["green", "blue"]) >>> setz = {'blue'} >>> setb = setx - setz >>> print(setb) {'green'}

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Sets

Subset and Superset

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ALI TAHERI - FUNDAMENTALS OF PROGRAMMING [PYTHON] Spring 2019

>>> setx = set(["green", "blue"]) >>> sety = set(["blue", "yellow"]) >>> issubset = setx <= sety >>> print(issubset) False >>> issuperset = setx >= sety >>> print(issuperset) False >>> setx = set(["green", "blue"]) >>> sety = set(["blue", "green"]) >>> issubset = setx <= sety >>> print(issubset) True >>> issuperset = setx >= sety >>> print(issuperset) True