文件readlines()方法 (File readlines() Method)

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

readlines()方法是Python中的內置方法，用于從文件中獲取所有行，該方法與此對象(當前文件流/ IO對象)一起調用，并返回文件中所有可用的行，我們還可以指定從行讀取的總字節數。

Syntax:

句法：

    file_object.readlines(len)

Parameter(s):

參數：

• len – 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 all lines. If the len is greater than the total number of bytes of the file, then no more content will return.

  len –這是一個可選參數，可用于指定要從文件讀取的總字節數。 默認值為-1，表示所有行。 如果len大于文件的字節總數，則不會再返回任何內容。

Return value:

返回值：

The return type of this method is <class 'list'>, it returns the lines in the form of a list.

此方法的返回類型為<class'list'> ，它以列表形式返回行。

Example:

例：

# Python File readlines() 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, Indraloka\n")
myfile1.write("Urvarshi, 18, Indraloka\n")
myfile1.write("Menaka, 17, Indraloka\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  
# using readlines()
print("file's content (using readlines() method)...")
print("myfile1.readlines()...")
print(myfile1.readlines())
# reading a total number of bytes
# seeking file's position to 0th position
myfile1.seek(0)
# reads only 10 bytes
print("myfile1.readlines(10)...")
print(myfile1.readlines(10))
# reads next 300 bytes, if no more bytes
# method will not read more bytes
print("myfile1.readlines(300)...")
print(myfile1.readlines(300))
# closing the file
myfile1.close()

Output

輸出量

file's content (using readlines() method)...
myfile1.readlines()...
['Shivang, 21, Indore\n', 'Pankaj, 27, Mumbai\n', 'Rambha, 16,Indraloka\n', 'Urvarshi, 18, Indraloka\n', 'Menaka, 17, Indraloka\n']
myfile1.readlines(10)...
['Shivang, 21, Indore\n']
myfile1.readlines(300)...
['Pankaj, 27, Mumbai\n', 'Rambha, 16, Indraloka\n', 'Urvarshi,18, Indraloka\n', 'Menaka, 17, Indraloka\n']

翻譯自: https://www.includehelp.com/python/file-readlines-method-with-example.aspx