How to Write Content in a File using Python

Python has built-in support for performing operations like writing in a file, reading, removing, etc. I have written detailed tutorials covering these file operations:

In this tutorial, I am specifically explaining how to write content to a text file using Python.

Without importing any module, you may use the open() function, and depending on the requirements for writing the content, you may specify the mode as explained below.

Modes for opening a file for writing new content

Just to remind you, this is how open() function is used:

In the mode argument, you may specify the writing option as follows:

An example of Python write to file by ‘w’ value

In this example, first I opened the text file with the ‘r’ argument value for mode i.e. opening the text file in read mode to show the existing content.

This is followed by closing the file and reopening in the write mode by using the ‘w’ value.

Again, the file is opened by ‘r’ value, and the content of the file is displayed:

# A demo of writing content to text file

ReadTxtFile = open("write-demo.txt", "r")

txtContent = ReadTxtFile.read();

print ("Existing Content : ", txtContent)

ReadTxtFile.close()

#File in write mode

WriteTxtFile = open("write-demo.txt", "w")

WriteTxtFile.write ("This is new text for the \n demo of writing in text file.")


WriteTxtFile.close()


#Reopeing file in read mode

ReadPostWrite = open("write-demo.txt", "r")

ContPostWrite = ReadPostWrite.read();

print ("After write() : ", ContPostWrite)

ReadPostWrite.close()

The output:

You can see, the existing content is truncated and new content is added.

The example of write to text file in append mode

So, you do not want to lose existing content and just require adding the new content in the text file. This is where the append mode will work.

For append mode, use the ‘a’ value for the mode argument.

The example below demonstrates how:

# A demo of appending text


RTxtFile = open("write-append-demo.txt", "r")
txtCont = RTxtFile.read();
print ("Before Append - existing content : ", txtCont)

RTxtFile.close()

#File in append mode

AppendTxtFile = open("write-append-demo.txt", "a")
AppendTxtFile.write ("New text in append mode \n added to text file!")


AppendTxtFile.close()

#Reopeing file in read mode after append

ReasPostAppend = open("write-append-demo.txt", "r")
ContPostAppend = ReasPostAppend.read();
print ("After Append() : ", ContPostAppend)


ReasPostAppend.close()

You can see, the existing content remains in the text file while new content is added at the end of that specified file.

The example of ‘w+’ value with the ‘With’ statement

The ‘with’ keyword is a control flow structure that simplifies the error handling in Python.

In this example, I used the ‘w+’ value for the mode argument; which allows reading and writing operations.

The open function is used in the ‘with’ keyword that itself handles the file closing.

# A demo of w+ with 'With' keyword

with open('with-write-demo.txt', 'w+') as fileObject:

    txtFileCont = fileObject.read()
    print("Before writing: ", txtFileCont)
    fileObject.write('The new content is added to the text file!')
    fileObject.seek(0)  #Move pointer at the beginning of text file
    txtFileCont = fileObject.read()

    print("After Writing: ", txtFileCont)

The output of above example:

If file does not exist, a new file is created and as the final call is made for reading the content, it displays only what we wrote by the write() function.

The seek(0) is used to move the pointer at the beginning of the file, otherwise, an empty string is returned.

Using print function for writing in a file

Rather than displaying a line on the screen, you may also write to the file by specifying a file in the print function.

The following example shows writing a line to a text file using the print function:

# Writing by print function

with open('print-write.txt', 'w') as objFile:

    print('Writing a line by print function!', file=objFile)

Similarly, you may append the text by using the ‘a’ value for keeping existing content in the text file.

Writing a list to the text file by writelines() method

So, you may use a list in the writelines() for writing its items in the text file.

# Writing by writelines function


fileObject = open("list-write-demo.txt", "w+")

lstStrings = ["Python ", "Hello ", "World!"]
line = fileObject.writelines( lstStrings )


fileObject.seek(0)  #Move pointer at the beginning of text file
txtFileCont = fileObject.read()
print("After Writing: ", txtFileCont)


# Close the file
fileObject.close()

The output: