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In our last article, we have explained how to read an existing file on the disk. In this tutorial, we are going to explain how to write a file on disk. But before we write a file, we must open it by using the open() function. Let us read about the open() function and how we can use it.

• Calling the open() function to open a file to write


In order to perform file operations, we could call the open() function of io module, which is a default module for performing file operations. Using the open() function, we could provide a location of the file on the disk and a specific mode in which the file will be opened.

Let us take a look at a general syntax of open() function to open a file.



open('filename', mode);



• filename(a string value), is the name of file on which we are going to open and perform the file operation.
• mode(a string value), is a single or multiple file modes in which we are going to open a file.

Let's read about the required file mode value, to write the content of a file.






• Writing a file


Let's look at the mode required to write a file.



File Mode	Description
w	Searches for the file and opens it in write mode. If the file is found, its contents are overwritten. If file is not found, a new file is created. Allows you to write to the file.








• Methods to write to a file


We can write the contents of a file using the methods available to all the file objects. Let us take a look at these methods.



Methods	Description
write(str)	The write() method writes a string(str) value to a file.
writelines(lines)	The writelines() method writes a list of lines to a file.






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• Writing to a file using write() method


Let us see a program to write some already initialized string values to a file by using the write() method. This file will be created in the current directory(the same directory where we are going to store the upcoming Python program.).



# Python - Creating a file for performing for the write operation.
 


# Calling the open() function to open a file named File1.txt in write mode
file = open('File1.txt', 'w')


# Creating 3 strings and appending the newline character \n at their end
str1 = 'Hello World! \n'
str2 = 'Welcome to DecodeJava \n'
str3 = 'Hope you like our tutorials \n'


# Writing the first string value to the file using the write() method of file object
file.write(str1)


# Writing the second value to the file using the write() method of file object
file.write(str2)


# Writing the third string value to the file using the write() method of file object
file.write(str3)


# Closing the file after completing the write operation on it
file.close()




Output


Executing this program will create a file named File1.txt in the current directory, with its content-



Hello World!
Welcome to DecodeJava!
Hope you like our tutorials.








• Writing a file by taking input from user at console


Let us see a code to write to a file on disk by taking input from the user at the console, using the built-in input() function This file will be created in the current directory(the same directory where we are going to store the upcoming Python program.).



# Python - Writing a file by taking input from user at console
 


# Calling the open() function to open a file named File2.txt in write mode
file = open('File2.txt', 'w')


# Creating 3 strings
str1 = input('What is the capital of Finland? : ')
str2 = input('What is tallest building in the world? : ')
str3 = input('What is the densest forst in the world? : ')


# Writing the first string value to the file using the write() method of file object
file.write(str1 + '\n')


# Writing the second value to the file using the write() method of file object
file.write(str2 + '\n')


# Writing the third string value to the file using the write() method of file object
file.write(str3 + '\n')


# Closing the file after completing the write operation on it
file.close()




Output




What is the capital of Finland? : Helsinki
What is tallest building in the world? : Burj Khalifa
What is the densest forst in the world? : Amazon Basin



Executing this program will create a file named File2.txt in the current directory, with its content taken from the input typed by the user at the console such as -

File2.txt

Helsinki
Burj Khalifa
Amazon Basin








• Writing to a file using writelines() method


Let us see a program to write a list of lines(where each line is a string value), to a file on disk by usign the writelines() method.



# Python - Writing to a file using writelines() method
 


# Calling the open() function to open a file named File3.txt in write mode
file = open('File3.txt', 'w')


# Creating 3 strings and appending the newline character \n at their end
str1 = 'Hello World! \n'
str2 = 'Can you answer a question? \n'
str3 = 'Which came first - Chicken or Egg? \n'


# Creating a list of lines, where each line is a string value.
a_list = [str1, str2, str3]


# Writing a list of lines to the file using the writelines() method of file object
file.writelines(a_list)


# Closing the file after completing the write operation on it
file.close()




Output


Executing this program will create a file named File3.txt in the current directory, with its content-



Hello World! 
Can you answer a question? 
Which came first - Chicken or Egg? 



Note: We can even use the w+(write plus read mode), which allows us to not write to a file but also read its content For more on it, you will have to read our article, how to modify a file in Python.

In the next tutorial, we are going to explain how to append to the end of an existing file.






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