File handling in Python
In Python there is no need to import any external libraries for file handling as it comes with an inbuilt library There are 3 main operations associated with the file. 1. Creating/Opening a file. 2. Writing into the file/ Reading from the file. 3. Closing a file.
Step 1: Creating Opening a file :
Syntax :
filePtr = open("your_file_name.txt", "mode")
Following are the modes supported in python:
1. “w”, “r”, “a”: To open files in write mode, read mode and append mode respectively.
ex:
filePtr = open("my_file.txt", "w")
It will create a new file if the given file name doesn't exist else it will overwrite the contents of the given file.
filePtr = open("my_file.txt", "r")
It will open a file only if it exists in the reading mode. i.e. we cannot edit the contents of the file.
filePtr = open("my_file.txt" , "a")
It will append the contents of the file if already exists else it will create a new one.
- “w+”, “r+”, “a+” : To open a file in write and read mode, read and write mode, and append and read mode.
filePtr = open("my_file.txt", "w+")
It will create a new file if the given file name doesn't exist else it will overwrite the contents of the given file. In this mode, we can also read the content of the file at the same time.
filePtr = open("my_file.txt", "r+")
It will open a file only if it exists in the reading mode also we can edit the contents of the file unlike in “r” mode.
** Note: +r differs from +w mode as in +r mode it doesn't delete the content also it doesn't create a new file if doesn't exist.**
filePtr = open("my_file.txt" , "a+")
It will allow simultaneous read and append operation on the file.
- “wb”, “rb”, “ab”: To open files in write, read and append in binary mode respectively.
ex:
filePtr = open("my_file.txt", "wb")It will create a new file if the given file name doesn't exist else it will overwrite the contents of the given file.
filePtr = open("my_file.txt", "rb")
It will open a file only if it exists in the reading mode. i.e. we cannot edit the contents of the file.
filePtr = open("my_file.txt" , "ab")
It will append the contents of the file if already exists else it will create a new one.
- “wb+”, “rb+”, “ab+” : To open a file in write and read, **read and write **, and append and read in binary mode.
filePtr = open("my_file.txt", "wb+")
It will create a new file if the given file name doesn't exist else it will overwrite the contents of the given file. In this mode, we can also read the content of the file at the same time.
filePtr = open("my_file.txt", "rb+")
It will open a file only if it exists in the reading mode also we can edit the contents of the file unlike in “r” mode.
filePtr = open("my_file.txt" , "ab+")
It will allow simultaneous read and append operation on the file.
Step 2: Writing in a file/ Reading from the file:
We can write in a file using write() function
Syntax :
filePtr.write("THIS is a file CONTENT")
We can read from the file using read() and readline() function
ex:
content = filePtr.read(): This return the entire content of the file.
content = filePtr.readline(): This returns only the content of one line in a file.
Step 3: Closing a file
Closing a file is very important as if it exceeds the top limit it can lead to the crashing of the program. So it is advisable to close a file.
Syntax :
filePtr.close()