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Today, I would like to share with you the relevant knowledge of what the method of reading and writing python documents is, the content is detailed, and the logic is clear. I believe most people still know too much about this knowledge, so share this article for your reference. I hope you can get something after reading this article.

Foreword:

In Python, to manipulate a file, you just need to open the file using the built-in open function. The open function takes a file name and open mode as arguments and returns a file object. The engineer manipulates the file through the file object, and when it is finished, call the close method of the file object to close the file.

Create a new opentest.py:

F = open ('log.log') print (f.read ()) f.close ()

Output:

2022-02-17 13-13-41-41-14-74-7-9-6-14-14-12-12-14-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-17 13-14-14-12-14 13-14-14-14-12-12-17 13-13-14-14-12-12-17 13-12-17 13-13-14-14-12-17 13-12-17 13-12-17 13-12-17 13-12-17 13-12-17 13-12-17 13-12-17 13-12-17 13-12-17 13-12-17 13

2022-02-17 13-13-41-41-34-797-WARNING-WARNINGRAPHY

2022-02-17 13-13-41-41-14-7-7-7-7-4-7-7-7-4-7-7-7-4-7-7-4-7-7-4-4-7-7-4-7-7-7-4-7-7-7-7-7-7-14-12-14 13-13-14-14-13-13-14-13-13-14-13-13-13-14-12-17 13-12-17 13-12-17 13-12-17 13-12-17 13-12-17 13-13-17 13-13-17 13-17 13-17 13-17 13-17 13-13-17 13-13-17 13-13-17 13-13-17 13-13-17 13-13-17 13-13-17 13

2022-02-17 13 Flux 41 purl 34 quot; 797 Vol. CRITICALL Vol critical

The open function opens in'r 'mode by default, or you can specify the open mode of the file.

'r': opens the file in read mode by default, and throws a FileNotfoundError exception if the file does not exist

'w': open the file in write mode, if the text {Niu is not empty, the existing contents of the file will be emptied, and if the file does not exist, create the file

'x': create a new file and throw a FileExistsError exception if the file already exists

'a': append the file to the end of the file

F = open ('log.log','w') f.write (' hello') f.close ()

Log.log file content

Hello

F = open ('log.log','a') f.write (' world') f.close ()

Log.log file content

Helloworld

In a computer program, each file opened needs to occupy a file handle, and a process has a limited number of file handles. In addition, the file handle will also take up the resources of the operating system, so when writing a program to process the file, you should pay attention to closing the file in time after the file processing is finished. File handle disclosure is perhaps the most common resource leakage problem and the most common mistake made by engineers. To avoid opening the file without closing it in time, finally is used in most programming languages to close the file handle. In Python, you can also use the find statement to ensure that the file will be closed no matter what the circumstances.

Try: F = open ('log.log','a') f.write (' world') finally: f.close ()

There is also a more concise and elegant way to write it in Python, even with the context manager

With open ('log.log') as f: print (f.read ())

As you can see, the number of lines of code becomes smaller after using the context manager. In Python, if you want to write code succinctly and gracefully, you should keep the number of lines of code as small as possible while ensuring readability.

Python provides three read-related functions, namely read and readline readlines, which serve the following purposes:

1. Read: read everything in the file

2. Readline: read one line at a time

3. Readlines: save the contents of the file to a list, and each line in the list corresponds to a line in the file.

With open ('log.log') as f: print (f.read ()) f.seek (0) # File read offset to the beginning of print (f.readline ()) f.seek (0) print (f.readlines ())

Output:

2022-02-17 13-13-41-41-14-74-7-9-6-14-14-12-12-14-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-17 13-14-14-12-14 13-14-14-14-12-12-17 13-13-14-14-12-12-17 13-12-17 13-13-14-14-12-17 13-12-17 13-12-17 13-12-17 13-12-17 13-12-17 13-12-17 13-12-17 13-12-17 13-12-17 13-12-17 13

2022-02-17 13-13-41-41-34-797-WARNING-WARNINGRAPHY

2022-02-17 13-13-41-41-14-7-7-7-7-4-7-7-7-4-7-7-7-4-7-7-4-7-7-4-4-7-7-4-7-7-7-4-7-7-7-7-7-7-14-12-14 13-13-14-14-13-13-14-13-13-14-13-13-13-14-12-17 13-12-17 13-12-17 13-12-17 13-12-17 13-12-17 13-13-17 13-13-17 13-17 13-17 13-17 13-17 13-13-17 13-13-17 13-13-17 13-13-17 13-13-17 13-13-17 13-13-17 13

2022-02-17 13 Flux 41 purl 34 quot; 797 Vol. CRITICALL Vol critical

2022-02-17 13-13-41-41-14-74-7-9-6-14-14-12-12-14-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-12-17 13-14-14-12-14 13-14-14-14-12-12-17 13-13-14-14-12-12-17 13-12-17 13-13-14-14-12-17 13-12-17 13-12-17 13-12-17 13-12-17 13-12-17 13-12-17 13-12-17 13-12-17 13-12-17 13-12-17 13

['2022-02-17 1314 147ERRORV error 796,' 2022-02-1713131RV 344JLV 34JLV 31RV error, '2022-02-17 131RV 34JV 34JLV 31RV error,' 2022-02-17 131RV 34JV 34JT 797 ERRORRT error

Python provides two write functions, write and writelines, which differ as follows:

1. Write: write the string to the file and return the number of characters written

2. Writelines: write a list of strings to the file.

With open ('log.log','w') as f: f.write (' hello') f.writelines (['\ njohn is good man','\ nsan is bad man'])

Log.log content

Hellojohn is good mansan is bad man

Each line in the file is processed in turn in units of behavior.

With open ('log.log') as f: for line in f: print (line,end= ") these are all the contents of the article" what is the method of reading and writing python files? "Thank you for reading! I believe you will gain a lot after reading this article. The editor will update different knowledge for you every day. If you want to learn more knowledge, please pay attention to the industry information channel.

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