Can we read and write in same file python?
Every open file has an implicit pointer which indicates where data will be read and written. Normally this defaults to the start of the file, but if you use a mode of Show Whenever you read or write N characters, the read/write pointer will move forward that amount within the file. I find it helps to think of this like an old cassette tape, if you remember those. So, if you executed the following code:
... It should end up printing You can use the
... Then you'll find that the file now contains All this applies on Unix systems, and you can test those examples to make sure. However, I've had problems mixing In summary, if you want to read/write from the middle of a file in Windows I'd suggest always using an explicit One final point - if you're specifying paths on Windows as literal strings, remember to escape your backslashes:
Or you can use raw strings by putting an
Or the most portable option is to use
You can find more information about file IO in the official Python docs. Python provides inbuilt functions for creating, writing, and reading files. There are two types of files that can be handled in python, normal text files and binary files (written in binary language, 0s, and 1s).
In this article, we will be focusing on opening, closing, reading, and writing data in a text file. File Access Modes Access modes govern the type of operations possible in the opened file. It refers to how the file will be used once its opened. These modes also define the location of the File Handle in the file. File handle is like a cursor, which defines from where the data has to be read or written in the file. There are 6 access modes in python.
How Files are Loaded into Primary Memory There are two kinds of memory in a computer i.e. Primary and Secondary memory every file that you saved or anyone saved is on secondary memory cause any data in primary memory is deleted when the computer is powered off. So when you need to change any text file or just to work with them in python you need to load that file into primary memory. Python interacts with files loaded in primary memory or main memory through “file handlers” ( This is how your operating system gives access to python to interact with the file you opened by searching the file in its memory if found it returns a file handler and then you can work with the file ). Opening a File It is done using the open() function. No module is required to be imported for this function. File_object = open(r"File_Name","Access_Mode") The file should exist in the same directory as the python program file else, the full address of the file should be written in place of the filename. Note: The r is placed before the filename to prevent the characters in the filename string to be treated as special characters. For example, if there is \temp in the file address, then \t is treated as the tab character, and an error is raised of invalid address. The r makes the string raw, that is, it tells that the string is without any special characters. The r can be ignored if the file is in the same directory and the address is not being placed. Python
Here, file1 is created as an object for MyFile1 and file2 as object for MyFile2 Closing a file close() function closes the file and frees the memory space acquired by that file. It is used at the time when the file is no longer needed or if it is to be opened in a different file mode. File_object.close() Python
Writing to a file There are two ways to write in a file.
File_object.write(str1)
File_object.writelines(L) for L = [str1, str2, str3] Reading from a file There are three ways to read data from a text file.
File_object.read([n])
File_object.readline([n])
File_object.readlines() Note: ‘\n’ is treated as a special character of two bytes Python3
Output: Output of Read function is Hello This is Delhi This is Paris This is London Output of Readline function is Hello Output of Read(9) function is Hello Th Output of Readline(9) function is Hello Output of Readlines function is ['Hello \n', 'This is Delhi \n', 'This is Paris \n', 'This is London \n'] Appending to a file Python3
Output: Output of Readlines after appending ['This is Delhi \n', 'This is Paris \n', 'This is London \n', 'Today \n'] Output of Readlines after writing ['Tomorrow \n']
This article is contributed by Harshit Agrawal. If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to . See your article appearing on the GeeksforGeeks main page and help other Geeks. Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above. Can two processes read and write to the same file?If you try to read at the same time someone else is writing, that's perfectly OK. The only issue is if you are trying to read a block that the writer is writing at the same time. In that cause, the data you get is unpredictable but you should be able to read.
Can you read and write to a file at the same time?It is possible to read and write the same file at different times, and it is possible to read one file and write another at the same time, but it isn't possible to read and write the same file at the same time.
Can I read a file while it is being written?Most likely, you'll have to make your program open the file, read a small chunk, close the file, and then wait for a bit before reading again. Even then, there's no guarantee that you won't have the file open when the writing process tries to write.
Are both reading and writing possible after opening a file if so how?'r+' opens the file for both reading and writing. On Windows, 'b' appended to the mode opens the file in binary mode, so there are also modes like 'rb', 'wb', and 'r+b'. Also reading then writing works equally well using 'r+b' mode, but you have to use f.
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