readline()方法從檔中讀取一個完整的行。結尾的換行符也保持在字串中。如果參數 size 存在且非負，這是一個最大字節數，包括結尾的換行和不完整的行可能被返回。
當遇到EOF，一個空字元串立即被返回。
語法
下麵是 readline()方法的語法-
fileObject.readline( size );
參數
-
size -- 這是從檔中讀取的位元組數。
返回值
此方法從檔中返回讀取的行。
示例
下麵的例子顯示 readline() 方法的使用。
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()
當我們運行上面的程式，會產生以下結果 -
Name of the file: foo.txt Read Line: This is 1st line Read Line: This
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