Python write to a file example

You can read a file line by line with these two methods. They are slightly different, so let's see them in detail. In contrast, readlines returns a list with all the lines of the file as individual elements strings. This is the syntax:. If you need to create a file "dynamically" using Python, you can do it with the "x" mode. With this mode, you can create a file and then write to it dynamically using methods that you will learn in just a few moments.

A curious thing is that if you try to run this line again and a file with that name already exists, you will see this error:. According to the Python Documentation , this exception runtime error is:. To modify write to a file, you need to use the write method. You have two ways to do it append or write based on the mode that you choose to open it with. Let's see them in detail. The "a" mode allows you to open a file to append some content to it.

And we want to add a new line to it, we can open it using the "a" mode append and then, call the write method, passing the content that we want to append as argument. This is the basic syntax to call the write method:. Sometimes, you may want to delete the content of a file and replace it entirely with new content.

You can do this with the write method if you open the file with the "w" mode. As you can see, opening a file with the "w" mode and then writing to it replaces the existing content. If you want to write several lines at once, you can use the writelines method, which takes a list of strings. Each string represents a line to be added to the file. Now you know how to create, read, and write to a file, but what if you want to do more than one thing in the same program?

Let's see what happens if we try to do this with the modes that you have learned so far:. How can we solve this? Very useful, right? This is probably what you will use in your programs, but be sure to include only the modes that you need to avoid potential bugs.

To remove a file using Python, you need to import a module called os which contains functions that interact with your operating system. Particularly, you need the remove function. This function takes the path to the file as argument and deletes the file automatically.

Context Managers are Python constructs that will make your life much easier. By using them, you don't need to remember to close a file at the end of your program and you have access to the file in the particular part of the program that you choose. If the code is not indented, it will not be considered part of the context manager. This context manager opens the names. This variable is used in the body of the context manager to refer to the file object.

After the body has been completed, the file is automatically closed, so it can't be read without opening it again. But wait! We have a line that tries to read it again, right here below:.

This error is thrown because we are trying to read a closed file. Awesome, right? The context manager does all the heavy work for us, it is readable, and concise. When you're working with files, errors can occur. Sometimes you may not have the necessary permissions to modify or access a file, or a file might not even exist. As a programmer, you need to foresee these circumstances and handle them in your program to avoid sudden crashes that could definitely affect the user experience.

Let's see some of the most common exceptions runtime errors that you might find when you work with files:. According to the Python Documentation , this exception is:. For example, if the file that you're trying to open doesn't exist in your current working directory:. This is a huge advantage during the process of debugging. This is another common exception when working with files. This exception is raised when you are trying to read or modify a file that don't have permission to access.

If you try to do so, you will see this error:. This particular exception is raised when you try to open or work on a directory instead of a file, so be really careful with the path that you pass as argument. With this statement, you can "tell" your program what to do in case something unexpected happens. In this python tutorial, you will learn about Python write variable to file with examples.

Also, we will cover the below topics:. In this example, I will show two ways to write values of a variable in Python to a text file. Also you can check, Python write String to a file. I am taking three Python variables as carname, caryear, and carcolor, and assigning them a value and next to open a file. After opening the file, I used file. Here the contents are carname, caryear, and carcolor. Then use the file. Below image shows the output. Another function repr it is used to convert a variable in to string.

In the above example, I have used the repr function to convert a variable into string. After opening the file for each variable repr function is assigned. The following example shows writing a line to a text file using the print function :. The writelines method is used to write a sequence of strings to the file. So, you may use a list in the writelines for writing its items in the text file. The Headlines hide. Modes for opening a file for writing new content 2.

The example of Python write to text file in append mode 4. Using print function for writing in a file 6. Writing a list to the text file by writelines method. A demo of writing content to text file.

File in write mode. Reopeing file in read mode. A demo of appending text.