How to use the readlines() function to read all lines in a file in Python 2.x

How to use the readlines() function to read all lines in a file in Python 2.x

In Python programming, it is often necessary to read the contents of a file. Python provides a wealth of file operation functions, among which the readlines() function is a convenient method for reading all lines in a file. This article will detail how to read files using the readlines() function in Python 2.x.

The readlines() function is a method of the file object in Python that can be used to read all the lines in the file and return them in the form of a list. The following is the basic syntax for using the readlines() function:

file_object.readlines()

where file_object is the open file object.

The following example will demonstrate how to use the readlines() function to read all the lines in the file:

# 打开文件
file = open('example.txt', 'r')

# 读取所有行
lines = file.readlines()

# 输出每一行
for line in lines:
    print(line.strip())  # 使用strip()函数去除每行末尾的换行符

# 关闭文件
file.close()

In this example, first we use the open() function to open a file named example .txt file and operate in read-only mode 'r'. We then use the readlines() function to read all the lines in the file and store them in a list called lines. Next, we use a for loop to iterate through the lines list and print the contents of each line using a print statement. Before outputting, we also use the strip() function to remove the newline character at the end of each line.

Finally, we use the close() function to close the file and release system resources.

It should be noted that the readlines() function will read the contents of each line in the file as a string element and add them to the list. If there are many or long lines in the file, it may take up a lot of memory. Therefore, when processing large files, it is recommended to use the method of reading line by line instead of reading all lines at once.

When using the readlines() function to read a file, you can also use some other parameters to control the number of lines read. For example, readlines(10) will only read the first 10 lines of the file. This avoids reading the entire file into memory when working with large files.

Summary:

This article describes how to use the readlines() function in Python 2.x to read all lines in a file. By using this convenient function, we can easily obtain the contents of the file and perform subsequent processing. In practical applications, you also need to pay attention to the rational use of memory and avoid reading large files at once.

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