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中的一種內置方法，用于從文件中獲取一行，該方法與此對象(當前文件流/ IO對象)一起調用，并從文件中返回一行，我們還可以指定從行讀取的總字節數。
Syntax:
句法：
file_object.readline(bytes)
Parameter(s):
參數：
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 –這是一個可選參數，可用于指定要從文件讀取的總字節數。 它的默認值為-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.
該方法的返回類型為<class'str'> ，它返回字符串。
Example 1:
范例1：
# Python File readline() Method with Example
# creating a file
myfile1 = open("hello1.txt", "w")
# writing content in the file
myfile1.write("Shivang, 21, Indore\n")
myfile1.write("Pankaj, 27, Mumbai\n")
myfile1.write("Rambha, 16, Heaven\n")
# closing the file
myfile1.close()
# reading the file (opening file in 'r' mode)
myfile1 = open("hello1.txt","r")
# reading and printing the file's content
# line by line
print("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 position
myfile1.seek(0)
print("file's content (using read() method)...")
print(myfile1.read())
# closing the file
myfile1.close()
Output
輸出量
file's content (using readline() method)...
line1: Shivang, 21, Indore
line2: Pankaj, 27, Mumbai
line3: Rambha, 16, Heaven
file's content (using read() method)...
Shivang, 21, Indore
Pankaj, 27, Mumbai
Rambha, 16, Heaven
Example 2:
范例2：
# Python File readline() Method with Example
# creating a file
myfile1 = open("hello1.txt", "w")
# writing content in the file
myfile1.write("Shivang, 21, Indore\n")
myfile1.write("Pankaj, 27, Mumbai\n")
myfile1.write("Rambha, 16, Heaven\n")
# closing the file
myfile1.close()
# reading the file (opening file in 'r' mode)
myfile1 = open("hello1.txt","r")
# reading and printing the file's content
# line by line
print("file's content (using readline() method)...")
# reads whole line
print("line1: ", myfile1.readline(-1))
# reads 5 bytes
print("line2: ", myfile1.readline(5))
# reads next 10 bytes
print("line3: ", myfile1.readline(10))
# closing the file
myfile1.close()
Output
輸出量
file's content (using readline() method)...
line1: Shivang, 21, Indore
line2: Panka
line3: j, 27, Mum
翻譯自: https://www.includehelp.com/python/file-readline-method-with-example.aspx
