The Secrets of Python Loops: Mastering the Art of Traversal

for loop: traverse the sequence

The for loop is the most common way to traverse sequences (such as lists, tuples, strings). Its syntax is:

for item in sequence:
# 代码块

For example, to print all elements in the list:

# 创建一个列表
numbers = [1, 2, 3, 4, 5]

# 使用 for 循环遍历列表
for number in numbers:
print(number)

while loop: conditional traversal

While loops allow you to continue executing a block of code when a specific condition is met. Its syntax is:

while condition:
# 代码块

For example, to read user input until they enter "exit":

# 提示用户输入
user_input = input("输入内容：")

# 使用 while 循环不断读取直到用户输入 "exit"
while user_input != "exit":
print(user_input)
user_input = input("输入内容：")

Iterator: efficient traversal

python An iterator is a special object that can generate elements in a sequence one by one without storing the entire sequence. It allows you to iterate over large sequences without running out of memory.

To create an iterator you can use the function iter():

# 创建一个列表
numbers = [1, 2, 3, 4, 5]

# 创建一个迭代器
numbers_iter = iter(numbers)

# 访问迭代器的元素
print(next(numbers_iter))# 输出 1
print(next(numbers_iter))# 输出 2

List comprehension: concise traversal

List comprehensions provide a concise way to create new lists based on traversing existing sequences. Its syntax is:

new_list = [expression for item in sequence]

For example, to create a list of square numbers:

numbers = [1, 2, 3, 4, 5]

# 使用列表推导创建新列表
squared_numbers = [number ** 2 for number in numbers]

# 打印结果
print(squared_numbers)# 输出 [1, 4, 9, 16, 25]

Summarize

Mastering Python Loops are essential for efficiently processing elements in a sequence. By using for loops, while loops, iterators, and list comprehensions, you can easily iterate through data, satisfy conditions, and create new data structures. Taking full advantage of these tools will greatly improve your Python coding skills and problem-solving efficiency.

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