What are the ways to implement loop statements in Python?

In Python, there are several ways to implement loop statements:

1. for loop

The for loop is the most common in Python. One of the commonly used loop statements, which can traverse any sequence, such as a list or a string. The basic syntax is:

for variable in sequence:
    # 循环体

where variable represents the variable name and sequence represents the sequence to be traversed.

1.1 Traversing a list or tuple

Through the for loop, you can traverse each element in a list or tuple, and perform various operations, such as calculations, judgments, etc. For example:

numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
for number in numbers:
    print(number**2)

This program will output the square numbers from 1 to 10.

1.2 Traversing a string

Through the for loop, you can traverse each character in a string and perform various operations, such as calculations, judgments, etc. For example:

s = "hello world"
for char in s:
    print(char.upper())

This program will output each character in the string and convert it to uppercase letters.

1.3 Traversing the dictionary

Through the for loop, you can traverse each key-value pair in a dictionary and perform various operations, such as calculations, judgments, etc. For example:

d = {'apple': 2, 'banana': 3, 'orange': 4}
for key, value in d.items():
    print(key, value)

This program will output all key-value pairs in the dictionary.

1.4 Traverse file content

Through the for loop, you can traverse each line of content in a file and perform various operations, such as reading, writing, etc. For example:

with open('file.txt', 'r') as f:
    for line in f:
        print(line.strip())

This program will output each line in the file.

2. while loop

The while loop is used to execute a set of statements in a loop until the condition is not met. The basic syntax is:

2.1 List traversal through while loop:

fruits = ['apple', 'banana', 'orange', 'grape']
i = 0
while i < len(fruits):
    print(fruits[i])
    i += 1

This program will traverse all elements in the fruits list and output it.

2.2 Play a number guessing game through a while loop:

import random

number = random.randint(1, 10)
guess = 0
while guess != number:
    guess = int(input("猜一个 1-10 之间的数字："))
    if guess > number:
        print("猜大了！")
    elif guess < number:
        print("猜小了！")
    else:
        print("恭喜你，猜中了！")

This program will prompt the user to guess the number and give a hint when the guess is correct or wrong

while 条件:
    # 循环体

3. range () Function

range() function returns a sequence of numbers within a specified range, which can be used in a for loop. The basic syntax is:

range(start, stop, step)

3.1 Traverse a sequence of numbers within a certain range

for i in range(1, 11):
    print(i)

This program will output all numbers from 1 to 10.

3.2 Generate a list of integers

numbers = list(range(1, 11))
print(numbers)

This program will generate a list of integers from 1 to 10.

3.3 Traverse numbers within a certain range with a step size of 2

for i in range(1, 11, 2):
    print(i)

This program will output all odd numbers from 1 to 10.

3.4 Traverse the list with the len() function

fruits = ['apple', 'banana', 'orange', 'grape']
for i in range(len(fruits)):
    print(fruits[i])

This program will traverse all elements in the fruits list and output them in sequence.

4. enumerate() function

enumerate() function is used to combine a traversable data object into an index sequence, while listing the data and data subscripts. The basic syntax is:

for i, value in enumerate(sequence):
    # 循环体

The following is an example of using the enumerate() function:

numbers = [1, 2, 3, 4, 5]
for i, number in enumerate(numbers):
    print("索引位置：{}，对应的元素值：{}".format(i, number))

This program will traverse each element in the list numbers and output the index position of the element in the list and the corresponding value. The enumerate() function can also be used to find the position of an element in a list while looping. For example:

fruits = ['apple', 'banana', 'orange', 'grape']
for i, fruit in enumerate(fruits):
    if fruit == 'banana':
        print("banana 的位置是：", i)

This program will find the position of the element 'banana' in the fruits list and output its index position in the list.

The above is the detailed content of What are the ways to implement loop statements in Python?. For more information, please follow other related articles on the PHP Chinese website!