文件readline()方法 (File readline() Method)

readline() method is an inbuilt method in Python, it is used to get one line from the file, the method is called with this object (current file stream/IO object) and returns one line from the file, we can also specify the total number of bytes to read from the line.

readline()方法是Python中的一种内置方法，用于从文件中获取一行，该方法与此对象(当前文件流/ IO对象)一起调用，并从文件中返回一行，我们还可以指定从行读取的总字节数。

Syntax:

句法：

file_object.readline(bytes)

Parameter(s):

参数：

• bytes – It is an optional parameter and it can be used to specify the total number of bytes to read from the file. It's default value is -1 that specifies the whole line.

  bytes –这是一个可选参数，可用于指定要从文件读取的总字节数。 它的默认值为-1，用于指定整行。

Return value:

返回值：

The return type of this method is <class 'str'>, it returns the string.

该方法的返回类型为<class'str'> ，它返回字符串。

Example 1:

范例1：

# Python File readline() Method with Example# creating a filemyfile1 = open("hello1.txt", "w")# writing content in the filemyfile1.write("Shivang, 21, Indore\n")myfile1.write("Pankaj, 27, Mumbai\n")myfile1.write("Rambha, 16, Heaven\n")# closing the filemyfile1.close()# reading the file (opening file in 'r' mode)myfile1 = open("hello1.txt","r")# reading and printing the file's content  # line by lineprint("file's content (using readline() method)...")print("line1: ", myfile1.readline())print("line2: ", myfile1.readline())print("line3: ", myfile1.readline())# reading and printing the file's content# all at once using read() method# seeking the file position at 0th positionmyfile1.seek(0)print("file's content (using read() method)...")print(myfile1.read())# closing the filemyfile1.close()

Output

输出量

file's content (using readline() method)...line1:  Shivang, 21, Indoreline2:  Pankaj, 27, Mumbailine3:  Rambha, 16, Heavenfile's content (using read() method)...Shivang, 21, IndorePankaj, 27, MumbaiRambha, 16, Heaven

Example 2:

范例2：

# Python File readline() Method with Example# creating a filemyfile1 = open("hello1.txt", "w")# writing content in the filemyfile1.write("Shivang, 21, Indore\n")myfile1.write("Pankaj, 27, Mumbai\n")myfile1.write("Rambha, 16, Heaven\n")# closing the filemyfile1.close()# reading the file (opening file in 'r' mode)myfile1 = open("hello1.txt","r")# reading and printing the file's content  # line by lineprint("file's content (using readline() method)...")# reads whole lineprint("line1: ", myfile1.readline(-1))# reads 5 bytesprint("line2: ", myfile1.readline(5))# reads next 10 bytesprint("line3: ", myfile1.readline(10))# closing the filemyfile1.close()

Output

输出量

file's content (using readline() method)...line1:  Shivang, 21, Indoreline2:  Pankaline3:  j, 27, Mum

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