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This article is to share with you about how to use the Context Managers context manager in python, the editor thinks it is very practical, so I share it with you to learn. I hope you can get something after reading this article.

Create a new python file named py3_contextmanager.py, and write the operation code in this file:

# Context Managers context manager # is used to effectively manage resources. It has been mentioned before in file read and write operations # now take file read and write as an example # demonstrate Context Managers context manager # normal file write operations: F = open ('test.txt','w') f.write (' write data to file!') F.close () # is then done using Context Managers: with open ('test_new.txt','w') as f: f.write (' write data to file!') # here we don't write the operation of closing the file # because when we finish our own code operation and exit the # with context manager, the file will close automatically # the context manager usually closes the connection to the database # and you can also get operations such as releasing locks.

# next let's customize a context manager class # to open the file class Open_File (): # initialize the file name and the file opening mode def _ _ init__ (self,filename,mode): self.filename = filename self.mode = mode # set the actual operation of the context manager # Open the file def _ _ enter__ (self): self.file = open (self.filename) Self.mode) return self.file # when exiting Manager Execute the close file operation def _ _ exit__ (self,exc_type,exc_val,traceback): self.file.close () # use the context manager # with this line of code actually executes the two methods with Open_File ('sample.txt','w') as f: f.write (' testing') # we print the status of the file print (f.closed) # True

# next use the decorator to rewrite the above # Custom context Manager # you need to import the module contexlibfrom contextlib import contextmanager

@ contextmanagerdef open_file (file,mode): try: F = open (file,mode) yield f finally: f.close () # call manager with open_file ('sample_new.txt','w') as wf: wf.write (' write data!') Print (wf.closed)

# next, look at the operation import os in an os module.

# get the current working directory cwd = os.getcwd () # switch to the specified directory test1os.chdir ('test1') # list all the contents in this directory print (os.listdir ()) # switch back to the current working directory os.chdir (cwd)

# get the current working directory cwd = os.getcwd () # switch to the specified directory test2os.chdir ('test2') # list all the contents in this directory print (os.listdir ()) # switch back to the current working directory os.chdir (cwd) # We have to do the same thing many times # run and we get the following results: # [' test1.doc', 'test1.txt'] # [' test2.doc'' The code logic above 'test2.txt'] # is very suitable for # using context manager implementation # modified as follows: @ contextmanagerdef change_dir (destination): try: cwd = os.getcwd () os.chdir (destination) # where yield returns all yield finally: os.chdir (cwd) # call: with change_dir (' test1'): print (os.listdir ()) with change_dir ('test2'): print (os.listdir ())

This is how to use the Context Managers context manager in python. The editor believes that there are some knowledge points that we may see or use in our daily work. I hope you can learn more from this article. For more details, please follow the industry information channel.

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