๐ 1. Lists: The Universal Storage Box for Data
Programming Truth: Lists are the most widely used data structure in Python, capable of storing any type of data, like a mutable “magic array”! Life Scenario Analogy:
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List โ Train carriages (elements are passengers, who can get on and off at any time)
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Index โ Seat number (counting starts from 0)
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Operations โ Dispatcherโs control panel (add, delete, modify, query)
๐ ๏ธ 2. Creating Lists: Four Methods
1. Direct Creation Method
# Creating a list with different data typesfruits = ["apple", "banana", "orange"] # String listscores = [90, 85, 77, 93] # Integer listmixed = [1, "text", True, 3.14] # Mixed type listempty = [] # Empty list2. Constructor Method
numbers = list(range(5)) # [0,1,2,3,4]chars = list("Python") # ['P','y','t','h','o','n']3. List Comprehension (Detailed Explanation Tomorrow)
squares = [x**2 for x in range(5)] # [0,1,4,9,16]๐ 3. List Operations: The Four Kings of Add, Delete, Modify, Query
1. Add: Three Moves to Add Elements
animals = ["cat", "dog"]# Append elementanimals.append("rabbit") # Add to the end โ ["cat", "dog", "rabbit"]# Insert elementanimals.insert(1, "hamster") # Insert at index 1 โ ["cat", "hamster", "dog", "rabbit"]# Merge listsanimals.extend(["parrot", "goldfish"]) # โ ["cat", "hamster", "dog", "rabbit", "parrot", "goldfish"]2. Delete: Three Swords to Remove Elements
# Remove by valueanimals.remove("hamster") # Remove the first matching item โ ["cat", "dog", ...]# Remove by indexdel animals[0] # Remove element at index 0 โ ["dog", ...]popped = animals.pop(2) # Remove and return the element at index 2 ("rabbit")# Clear listanimals.clear() # Clear โ []3. Modify: Element Transformation Technique
colors = ["red", "green", "blue"]colors[1] = "yellow" # Modify index 1 โ ["red", "yellow", "blue"]colors[::2] = ["pink", "purple"] # Step modification โ ["pink", "yellow", "purple"]4. Query: Three Treasures to Locate Elements
nums = [10, 20, 30, 20]# Index queryprint(nums[0]) # 10 (first element)print(nums[-1]) # 20 (last element)# Slice queryprint(nums[1:3]) # [20, 30] (index 1 to 2)# Existence checkprint(30 in nums) # Trueprint(nums.index(20)) # 1 (index of first occurrence)print(nums.count(20)) # 2 (number of occurrences)โ ๏ธ 4. Beginner’s Pitfall Guide
Pitfall 1: Index Out of Bounds (IndexError)
lst = [1,2,3]print(lst[3]) # Error! Valid indices are 0-2Pitfall 2: Modifying Immutable Elements
nested = [1, [2,3], 4]nested[1][0] = 5 # Correct โ [1, [5,3], 4]nested[0] = [7,8] # Correct โ [[7,8], [5,3], 4]Pitfall 3: Shallow Copy Trap
a = [1,2]b = a # Reference the same listb.append(3)print(a) # [1,2,3] Synchronized modification!# Correct copyc = a.copy() # Method 1d = a[:] # Method 2๐ฎ 5. Practical Application: Student Grade Management System
students = []while True: print("\n1.Add 2.Delete 3.Modify 4.Query 0.Exit") choice = input("Please choose:") if choice == "1": name = input("Name:") score = float(input("Score:")) students.append([name, score]) elif choice == "2": name = input("Delete Name:") for s in students: if s[0] == name: students.remove(s) break elif choice == "3": name = input("Modify Name:") new_score = float(input("New Score:")) for s in students: if s[0] == name: s[1] = new_score elif choice == "4": print("\nCurrent Students:") for idx, (name, score) in enumerate(students, 1): print(f"{idx}. {name}๏ผ{score}") elif choice == "0": breakprint("System has exited")โ 6. Soul-Searching Questions
Q1: How to traverse a list in reverse?
for item in reversed([1,2,3]): print(item) # 3 2 1Q2: What is the difference between lists and tuples?โค Lists are mutable, tuples are immutable! Tuples are defined with ()
Q3: How to randomly shuffle a list?
import randomnums = [1,2,3,4]random.shuffle(nums) # e.g., [3,1,4,2]