Writing Files in Python

Python is a very popular programming language that provides a rich API for developers to use. Writing files is a very basic operation in Python. This article will introduce how to write files in Python.

Opening Files

In Python, use the open() function to open a file. It typically takes two arguments: the file name and the opening mode. The open() function returns a file object.

The following are some common modes:

• r: Read mode; the default value; an error occurs if the file does not exist.
• a: Append mode; a file is created if it does not exist.
• w: Write mode; a file is created if it does not exist; an error occurs if it exists.
• x: Create mode; an error occurs if the file already exists.
• b: Binary mode.
• t: Text mode (the default value).

Sample Code:

filename = "test.txt"
file = open(filename, "w")

The above code creates a file named test.txt (if it doesn’t exist) and then opens it in write mode.

If you don’t specify an open mode, the default open mode is r. If you want to open a file for non-text files (such as audio, images, etc.), for example, a binary audio file, you should use b mode.

filename = "audio.wav"
file = open(filename, "rb")

The above code creates a binary file named audio.wav and opens it in binary mode.

Writing to Files

Writing to files in Python is very simple. Now that we’ve opened the file, we can write data using the write() method. Note that the write() method only accepts strings, so if you want to write other types of data, you need to convert them to strings first.

Sample Code:

file.write("Hello World")

The above code writes the string “Hello World” to the file.

Similar to the write() method, file objects also have a writelines() method, which allows you to write multiple lines of data simultaneously.

Sample Code:

lines = ["line1", "line2", "line3"]
file.writelines(lines)

The above code will write three lines of data to the file.

After writing the file, you need to call the close() method to close the file object.

file.close()

Complete Example

The following is a complete example code that creates a file named test.txt and writes some data to it.

filename = "test.txt"
file = open(filename, "w")
file.write("This is a test file.n")
file.writelines(["line1n", "line2n", "line3n"])
file.close()

The above code writes the results to the file test.txt.

With Statement

In Python, you can use the with statement to open files. When you open a file using the with statement, the file object is automatically closed at the end of the code block. This means you don’t need to manually call the close() method.

Sample Code:

with open("test.txt", "w") as file:
file.write("This is a test file.")

This code block automatically closes the file object.

Conclusion

The Python programming language provides simple methods for working with files. We can open a file using the open() function, then write data using the write() method or the writelines() method. Finally, we close the file by calling the close() method. In all cases, we should always try to open files using the with statement, such as with open() as file:.