Python 3 File readline()用法及代码示例

描述

方法readline()从文件中读取一整行。尾随换行符保留在字符串中。如果 size 参数存在且非负，则它是包括尾随换行符在内的最大字节数，并且可能会返回不完整的行。

仅当立即遇到 EOF 时才返回空字符串。

用法

以下是语法readline()方法≫

fileObject.readline( size );

参数

size─ 这是要从文件中读取的字节数。

返回值

此方法返回从文件中读取的行。

示例

下面的例子展示了 readline() 方法的用法。

Assuming that 'foo.txt' file contains following text:
This is 1st line
This is 2nd line
This is 3rd line
This is 4th line
This is 5th line

#!/usr/bin/python3

# Open a file
fo = open("foo.txt", "r+")
print ("Name of the file:", fo.name)

line = fo.readline()
print ("Read Line:%s" % (line))

line = fo.readline(5)
print ("Read Line:%s" % (line))

# Close opened file
fo.close()

结果

当我们运行上面的程序时，它会产生以下结果——

Name of the file: foo.txt
Read Line:This is 1st line

Read Line:This