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Day 5: Dictionaries and String Manipulation
Master Python dictionaries and string operations with examples and exercises.
Dictionaries: Key-Value Pairs
A dictionary in Python is a collection of key-value pairs. It's similar to a real-life dictionary where you look up a word (key) to find its definition (value).
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student_grades = {
"Alice": 85,
"Bob": 92,
"Charlie": 78
}
print(student_grades)Here’s how you can create, access, add, and remove elements from a dictionary.
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# Accessing Values
print(student_grades["Alice"]) # Output: 85
# Adding a new student
student_grades["David"] = 90
print(student_grades)
# Removing a student
del student_grades["Charlie"]
print(student_grades)Iterating through dictionaries:
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for student, grade in student_grades.items():
print(f"{student}: {grade}")String Manipulation
Python provides powerful tools to work with strings. Let’s explore slicing, formatting, and other string methods.
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text = "Hello, World!"
print(text[0:5]) # Output: Hello
print(text[-6:]) # Output: World!String formatting using f-strings:
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name = "Alice"
age = 25
print(f"My name is {name} and I am {age} years old.")Some common string methods:
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text = " Python is Awesome! "
# Convert to uppercase
print(text.upper()) # Output: " PYTHON IS AWESOME! "
# Convert to lowercase
print(text.lower()) # Output: " python is awesome! "
# Remove whitespace
print(text.strip()) # Output: "Python is Awesome!"
# Replace text
print(text.replace("Awesome", "Cool")) # Output: " Python is Cool! "
# Split text into a list
print(text.split()) # Output: ['Python', 'is', 'Awesome!']Exercises for Day 5
Exercise 1: Create a Dictionary of Students and Grades
Write a program that:
- Creates a dictionary with student names as keys and their grades as values.
- Adds a new student to the dictionary.
- Removes a student from the dictionary.
- Prints all student names and their grades.
Exercise 2: Reverse a String
Write a program that:
- Takes a string as input.
- Reverses the string and prints it.
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# Example
Input: "Python"
Output: "nohtyP"Exercise 3: Word Frequency Counter
Write a program that:
- Takes a sentence as input.
- Counts the frequency of each word in the sentence using a dictionary.
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# Example
Input: "Python is fun and Python is easy"
Output: {'Python': 2, 'is': 2, 'fun': 1, 'and': 1, 'easy': 1}