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).
- Text files: In this type of file, each line of text is terminated with a special character called EOL (End of Line), which is the new line character (‘\n’) in Python by default. In the case of CSV(Comma Separated Files, the EOF is a comma by default.
- Binary files: In this type of file, there is no terminator for a line, and the data is stored after converting it into machine-understandable binary language, i.e., 0 and 1 format.
Refer to the below articles to get an idea about the basics of file handling.
Opening a File in Python
Opening a file refers to getting the file ready either for reading or for writing. This can be done using the open() function. This function returns a file object and takes two arguments, one that accepts the file name and another that accepts the mode(Access Mode). Now, the question arises what is the access mode? Access modes govern the type of operations possible in the opened file. It refers to how the file will be used once it’s opened. These modes also define the location of the File Handle in the file. The file handle is like a cursor, which defines where the data has to be read or written in the file. There are 6 access modes in Python.
Mode | Description |
|---|
| ‘r’ | Open text file for reading. Raises an I/O error if the file does not exist. |
| ‘r+’ | Open the file for reading and writing. Raises an I/O error if the file does not exist. |
| ‘w’ | Open the file for writing. Truncates the file if it already exists. Creates a new file if it does not exist. |
| ‘w+’ | Open the file for reading and writing. Truncates the file if it already exists. Creates a new file if it does not exist. |
| ‘a’ | Open the file for writing. The data being written will be inserted at the end of the file. Creates a new file if it does not exist. |
| ‘a+’ | Open the file for reading and writing. The data being written will be inserted at the end of the file. Creates a new file if it does not exist. |
| ‘rb’ | Open the file for reading in binary format. Raises an I/O error if the file does not exist. |
| ‘rb+’ | Open the file for reading and writing in binary format. Raises an I/O error if the file does not exist. |
| ‘wb’ | Open the file for writing in binary format. Truncates the file if it already exists. Creates a new file if it does not exist. |
| ‘wb+’ | Open the file for reading and writing in binary format. Truncates the file if it already exists. Creates a new file if it does not exist. |
| ‘ab’ | Open the file for appending in binary format. Inserts data at the end of the file. Creates a new file if it does not exist. |
| ‘ab+’ | Open the file for reading and appending in binary format. Inserts data at the end of the file. Creates a new file if it does not exist. |
Syntax:
File_object = open(r"File_Name", "Access_Mode")
Note: The file should exist in the same directory as the Python script, otherwise full address of the file should be written. If the file is not exist, then an error is generated, that the file does not exist.
Opening a file in read mode in Python
In this example, we are reading data from a Txt file. We have used read() to read the data.
Python3
file1 = open("myfile.txt")
print(file1.read())
file1.close()
|
Output:
Welcome to GeeksForGeeks!!
Note: In the above example, we haven’t provided the access mode. By default, the open() function will open the file in read mode, if no parameter is provided.
Adding data to the existing file in Python
If you want to add more data to an already created file, then the access mode should be ‘a’ which is append mode, if we select ‘w’ mode then the existing text will be overwritten by the new data.
Python3
file1 = open("myfile.txt" , "a" )
file1.write("\nWriting to file:)" )
file1.close()
|
Output:
Opening a file with write mode in Python
In this example, we are using ‘w+’ which deleted the content from the file, writes some data, and moves the file pointer to the beginning.
Python3
file = open('test.txt', 'w+')
file.write('Hello, world!')
file.seek(0)
data = file.read()
print(data)
file.close()
|
Output :
Hello World
Terminal Output
Reading Data from File Using Line By Line Using readline()
The readline() method in Python is used to read a single line from a file that has been opened for reading. When readline() is used in the code, it reads the next line of the file and returns it as a string.
In this example, we are reading data line by line from a file named test.txt and printing it into the terminal.
Python3
file = open('test.txt', 'r')
line = file.readline()
while line:
print(line)
line = file.readline()
file.close()
|
Test file
Output:
Terminal output