Python File fileno()用法及代码示例

文件 fileno() 方法

fileno() 方法是 Python 中的内置方法，用于获取文件编号，即文件描述符作为流的整数。如果操作系统不使用文件描述符关闭文件，它可能会返回错误。

用法:

    file_object.fileno()

参数：

• 它不接受任何参数。

返回值：

这个方法的返回类型是<class 'int'>，它返回一个整数值，它是文件的文件描述符。

范例1：

# Python File fileno() Method with Example

# creating two files
myfile1 = open("hello1.txt", "w")
myfile2 = open("hello2.txt", "w")

# printing the file descriptors
print("files are in write mode...")
print("myfile1.fileno():", myfile1.fileno())
print("myfile2.fileno():", myfile2.fileno())

# closing the files
myfile1.close()
myfile2.close()

# opening file in Read modes
myfile1 = open("hello1.txt", "r")
myfile2 = open("hello2.txt", "r")

# printing the file descriptors
print("files are in read mode...")
print("myfile1.fileno():", myfile1.fileno())
print("myfile2.fileno():", myfile2.fileno())

# closing the files
myfile1.close()
myfile2.close()

输出

files are in write mode...
myfile1.fileno(): 5
myfile2.fileno(): 6
files are in read mode...
myfile1.fileno(): 5
myfile2.fileno(): 6

范例2：

# Python File fileno() Method with Example

# creating a file
myfile1 = open("hello1.txt", "w")

# printing the file descriptor
print("myfile1.fileno():", myfile1.fileno())

# closing the files
myfile1.close()

# trying to print the file descriptor
# after closing the file
# error will be returned
# printing the file descriptor
print("myfile1.fileno():", myfile1.fileno())

输出

myfile1.fileno(): 5
Traceback (most recent call last): File "main.py", line 16, in <module>
    print("myfile1.fileno():", myfile1.fileno())
ValueError:I/O operation on closed file