48 - File handling in Python
#python #python3 #pythoncourse #file #filehandling
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Till now, we were taking the input from the console and writing it back to the console to interact with the user.
Sometimes, it is not enough to only display the data on the console. The data to be displayed may be very large, and only a limited amount of data can be displayed on the console since the memory is volatile, it is impossible to recover the programmatically generated data again and again.
The file handling plays an important role when the data needs to be stored permanently into the file. A file is a named location on disk to store related information. We can access the stored information (non-volatile) after the program termination.
The file-handling implementation is slightly lengthy or complicated in the other programming language, but it is easier and shorter in Python.
In Python, files are treated in two modes as text or binary. The file may be in the text or binary format, and each line of a file is ended with the special character.
Hence, a file operation can be done in the following order.
Open a file
Read or write - Performing operation
Close the file
Opening a file
Python provides an open() function that accepts two arguments, file name and access mode in which the file is accessed. The function returns a file object which can be used to perform various operations like reading, writing, etc.
The close() method
Once all the operations are done on the file, we must close it through our Python script using the close() method. Any unwritten information gets destroyed once the close() method is called on a file object.
We can perform any operation on the file externally using the file system which is the currently opened in Python; hence it is good practice to close the file once all the operations are done.
The syntax to use the close() method is given below.
SN Access mode Description
1 r It opens the file to read-only mode. The file pointer exists at the beginning. The file is by default open in this mode if no access mode is passed.
2 rb It opens the file to read-only in binary format. The file pointer exists at the beginning of the file.
3 r+ It opens the file to read and write both. The file pointer exists at the beginning of the file.
4 rb+ It opens the file to read and write both in binary format. The file pointer exists at the beginning of the file.
5 w It opens the file to write only. It overwrites the file if previously exists or creates a new one if no file exists with the same name. The file pointer exists at the beginning of the file.
6 wb It opens the file to write only in binary format. It overwrites the file if it exists previously or creates a new one if no file exists. The file pointer exists at the beginning of the file.
7 w+ It opens the file to write and read both. It is different from r+ in the sense that it overwrites the previous file if one exists whereas r+ doesn't overwrite the previously written file. It creates a new file if no file exists. The file pointer exists at the beginning of the file.
8 wb+ It opens the file to write and read both in binary format. The file pointer exists at the beginning of the file.
9 a It opens the file in the append mode. The file pointer exists at the end of the previously written file if exists any. It creates a new file if no file exists with the same name.
10 ab It opens the file in the append mode in binary format. The pointer exists at the end of the previously written file. It creates a new file in binary format if no file exists with the same name.
11 a+ It opens a file to append and read both. The file pointer remains at the end of the file if a file exists. It creates a new file if no file exists with the same name.
12 ab+ It opens a file to append and read both in binary format. The file pointer remains at the end of the file.
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