In Python, file writing refers to the process of creating a new file or modifying an existing one by storing data within it. This data can be diverse, ranging from simple text to complex data structures. Python provides various methods and functionalities for writing to files, allowing you to manage and manipulate file content effectively.
In Python, you can write to a text file by following these three steps:
You can skip the last step by using the with statement.
with open("example.txt", "w") as f:
f.write("Hello world!")
This piece of code creates a new file called example.txt and writes “Hello World” into it.
In this guide, you are going to learn the basics of writing to a file in Python.
To write to a file in Python, use these three steps:
The syntax for the open() function is as follows:
open(path_to_a_file, mode)
Where:
mode
specifies in which state you want to open the file. Use the mode ‘w’ to write to the file and ‘a’ to append to a file (add text to the end of the file).The open() function returns a file object. This file object has two useful methods for writing text to the file:
Let’s see how to use these file-writing methods.
The write() method takes a string argument. It writes this argument into the opened file.
For example, let’s create a list of strings and use the write() method to write each of the strings into the file using a for loop:
words = ["This ", "is ", "a ", "test"]
with open("example.txt", "w") as f:
for word in words:
f.write(word)
As a result, a file called example.txt is created with the following content:
This is a test
Notice how each string is written to the same line by default.
If you want to have each word appear on a separate line, write the line break character ‘\n’ after writing a string to the file.
For example:
words = ["This", "is", "a", "test"]
with open("example.txt", "w") as f:
for word in words:
f.write(word)
f.write("\n")
In the example.txt file the result looks like this:
This
is
a
test
This is one way to write into a file.
But in the case of multiple strings, you can use the writelines() method to write them all into a file on the same go.
The writelines() function takes an iterable object, such as a list, that contains strings to be written into the opened file.
For example, let’s repeat the above example using the writelines() method:
words = ["This ", "is ", "a ", "test"]
with open("example.txt", "w") as f:
f.writelines(words)
After running this piece of code, the example.txt file looks like this:
This is a test
Now you know how to write text to a file in Python.
Next, let’s take a look at how to add text at the end of an already-existing text file.
To add text at the end of a file after the existing lines of text, use the write mode ‘a’.
This mode is called the appending mode. Appending means adding to the end of something.
For example:
# Let's first write to a file
with open("example2.txt", "w") as f:
f.write("This is ")
# Then let's reopen the file and append some text to it:
with open("example2.txt", "a") as f:
f.write("just another test.")
Here the result is a file called example2.txt with the following contents:
This is just another test.
As you can see, the last bits of text were successfully added to the end of the text file.
In this tutorial you learned how to write a file in Python.
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