How to use the readlines() function to read all lines in a file in Python 3.x

Python is a very popular programming language that provides many powerful functions and tools for working with files. In Python 3.x version, we can use readlines() function to read all the lines in the file. This article will introduce how to use the readlines() function to read files and provide relevant code examples.

The readlines() function is one of the built-in functions in Python. It can read all lines from a file and return a list containing all lines. We can achieve this functionality by calling this function on the file object. Here is a basic example of using the readlines() function:

file_path = 'example.txt'  # 文件路径

# 打开文件
with open(file_path, 'r') as file:
    lines = file.readlines()  # 使用readlines()函数读取所有行

# 遍历所有行并打印
for line in lines:
    print(line.strip())  # 使用strip()函数去除行末尾的换行符

In this example, we first define the path to the file and open the file using the with statement. Use 'r' mode to open the file, which means we want to open the file in read-only mode. Next, we call the readlines() function on the file object to read all the lines and store them in a variable called lines.

We then use a for loop to iterate through the lines list and print each line using the print() function. To remove the newline character at the end of each line, we use the strip() function.

It should be noted that the readlines() function stores each line of the file as a string in the list, and each line ends with a newline character (
). Therefore, before printing each line, we use the strip() function to remove the trailing newline character.

In addition to the above basic usage, the readlines() function can also accept a parameter size to specify the number of bytes to read. If this parameter is not specified, the entire contents of the file will be read by default.

The following is a sample code that uses the readlines() function to read part of the content:

file_path = 'example.txt'  # 文件路径

# 打开文件
with open(file_path, 'r') as file:
    lines = file.readlines(10)  # 读取前10个字节的内容

# 遍历并打印行
for line in lines:
    print(line.strip())  

In this example, we specify a parameter 10 in the readlines() function, indicating that we want to read Get the first 10 bytes of the file. Then, we loop through and print the lines we read.

Through the above example, we can see how to use the readlines() function in Python to read all lines in a file. This function is very simple and practical, and can quickly read files and store data in the form of a list. Reading all lines in a file is one of the common operations in file processing, so mastering the use of the readlines() function is very important for writing Python programs.

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