readline()方法从文件中读取一整行。尾部的换行符保持在字符串中。如果大小参数且非负，那么一个最大字节数，包括结尾的换行和不完整的行可能会返回。

遇到EOF时立即返回一个空字符串。

语法

以下是readline()方法的语法：

fileObject.readline( size );

参数

size -- 这是可以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。

例子

下面的例子显示了readline()方法的使用。

#!/usr/bin/python # Open a file fo = open("foo.txt", "rw+") print "Name of the file: ", fo.name # Assuming file has following 5 lines # This is 1st line # This is 2nd line # This is 3rd line # This is 4th line # This is 5th line line = fo.readline() print "Read Line: %s" % (line) line = fo.readline(5) print "Read Line: %s" % (line) # Close opend file fo.close()

当我们运行上面的程序，它会产生以下结果：

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