python 示例_带有示例的Python File open（）方法

python 示例

文件open()方法 (File open() Method)

open() method is an inbuilt method in Python, it is used to create, open or append a file.

open()方法是Python中的内置方法，用于创建，打开或附加文件。

Syntax:

句法：

    file_object = open(file_name, file_mode)

Parameter(s):

参数：

file_name – It is used to specify the file name.
file_name –用于指定文件名。
file_mode – It is an optional parameter, it is used to specify the various file modes.
file_mode –这是一个可选参数，用于指定各种文件模式。
- w – Opens the file in write mode i.e. creates a file.
- w –以写模式打开文件，即创建文件。
- r – Opens the file in reading mode.
- r –以读取模式打开文件。
- a – Opens the file in append mode.
- a –以追加模式打开文件。
- x – Creates the file, if file exists it returns an error.
- x –创建文件，如果文件存在则返回错误。
- t – It is used to file modes to specify the text mode (Example: wt, rt, at, and xt).
- t –用于文件模式以指定文本模式(例如： wt ， rt ， at和xt )。
- b – It is used to file modes to specify the binary mode (Example: wb, rb, ab, and xb).
- b –用于文件模式以指定二进制模式(例如： wb ， rb ， ab和xb )。

Return value:

返回值：

The return type of this method is <class '_io.TextIOWrapper'>, it returns a file object.

该方法的返回类型为<class'_io.TextIOWrapper'> ，它返回一个文件对象。

Example 1:

范例1：

# Python File open() Method with Example
print("creating files...")
# creating a file without specifying mode (b or t)
file1 = open("hello_1.txt", "w")
# creating a file in binary mode
file2 = open("hello_2.txt", "wb")
# creating a file in text mode
file3 = open("hello_3.txt", "wt")
print("file creation operation done...")
# printing the details of file objects
print(file1)
print(file2)
print(file3)

Output

输出量

creating files...
file creation operation done...
<_io.TextIOWrapper name='hello_1.txt' mode='w' encoding='UTF-8'>
<_io.BufferedWriter name='hello_2.txt'>
<_io.TextIOWrapper name='hello_3.txt' mode='wt' encoding='UTF-8'>

Example 2:

范例2：

# Python File open() Method with Example
# creating a file
f = open("hello.txt", "w")
print("file created...")
print(f) # prints file details
# opening created file in read mode
f = open("hello.txt", "r")
print("file opened...")
print(f) # prints file details
# opening file in append mode 
f = open("hello.txt", "a")
print("file opened in append mode...")
print(f) # prints file details

Output

输出量

file created...
<_io.TextIOWrapper name='hello.txt' mode='w' encoding='UTF-8'>
file opened...
<_io.TextIOWrapper name='hello.txt' mode='r' encoding='UTF-8'>
file opened in append mode...
<_io.TextIOWrapper name='hello.txt' mode='a' encoding='UTF-8'>

Example 3:

范例3：

# Python File open() Method with Example
# opening a file that doesn't exist
f = open("myfile.txt") # returns an error

Output

输出量

Traceback (most recent call last):
File "main.py", line 4, in <module>
f = open("myfile.txt") # returns an error
FileNotFoundError: [Errno 2] No such file or directory: 'myfile.txt'