In this Python tutorial, you will learn about Python write variable to file with examples.
Writing a variable to a file in Python can be done using several different methods. The most common method is to use the open function to create a file object, and then use the write method to write the contents of a variable to the file.
Using the repr() function
Using the pickle.dump() function
Using the string formatting
Using the str() function
Method-1: Python write variable to file using the repr() function
The repr() function in Python can also be used to convert a variable to a string before writing it to a file. The repr() function returns a string containing a printable representation of an object.
This can be useful if you want to write a variable to a file and also maintain the original format of the variable.
# Declaring variables for car name, year, and color carname="Swift" caryear="2000" carcolor="white" # Opening a file named "car.txt" in write mode file = open("car.txt", "w") # Using the repr() function to convert the string values to their string representation carname = repr(carname) caryear = repr(caryear) carcolor = repr(carcolor) # Writing the car name, year, and color to the file, with appropriate labels file.write("Car Name = " + carname + "\n" +"Car Year = "+caryear + "\n"+"Car color wp-block-image">write variable to a file in Python
Read: Get current directory Python
Method-2: Python write variable to file using the pickle.dump() function
The pickle module in Python provides dump() function, which can be used to write a variable to a file in a way that allows the variable to be easily restored later.
The dump() function takes two arguments: the variable to be written to the file and the file object to which the variable should be written.
# This code imports the pickle module import pickle # This line creates a dictionary variable named "student" student = # This line opens a file named "student.p" in write binary mode (wb) file = open('student.p', 'wb') # This line writes the "student" dictionary to the "student.p" file using the pickle.dump() function pickle.dump(student, file) # This line closes the "student.p" file file.close()
The above code creates a dictionary variable named “student” and stores some student information in it.
Then, it uses the pickle module to write the “student” dictionary to a file named “student.p” in binary format.
The pickle.dump() function is used to write the dictionary object to the file and the file.close() function is used to close the file after the data is written.
The conversion output is the form of the below image.
To read the data from the file “student”, use the below code.
# This code imports the pickle module import pickle # This line opens a file named "student.p" in read binary mode (rb) file = open('student.p', 'rb') # This line loads the data from the "student.p" file and assigns it to the "student" variable using the pickle.load() function student = pickle.load(file) # This line closes the "student.p" file file.close() # This line prints the contents of the "student" variable print(student)
The above code imports the pickle module and then uses it to read a file named “student.p” which is in binary format, using the pickle.load() function.
The pickle.load() function reads the data from the file and assigns it to the “student” variable.
Then the file.close() function is used to close the file after the data is read. Finally, the print(student) statement is used to print the contents of the “student” variable.
Method-3: Python write variable to file using the string formatting
Python provides several ways to format strings, one of which is using string formatting. This method allows you to insert values of variables into a string, which can then be written to a file.
# This code creates a set variable named "carname" with the value "figo" carname = # This line opens a file named "car.txt" in write mode (w) file = open("car.txt", "w") # This line uses string formatting to write the "carname" variable and its value to the file file.write("%s = %s\n" %("carname",carname)) # This line closes the "car.txt" file file.close()
The above code creates a set variable named “carname” and assigns the value “figo” to it.
Then, it opens a file named “car.txt” in write mode (w) and writes the “carname” variable and its value to the file using string formatting.
The file.write(“%s = %s\n” %(“carname”,carname)) statement is used to write the “carname” variable and its value to the file.
The %s is used as a placeholder for the variable name and the %s\n is used as a placeholder for the variable value.
The \n is used to add a new line after the value so that the next string written to the file will be in a new line. Finally, the file.close() function is used to close the file after the data is written.
Method-4: Python write variable to file using the str() function
The str() function in Python is used to convert any data type to a string. It can be used to convert objects of built-in types such as integers, floating-point numbers, and complex numbers to strings, as well as objects of user-defined types.
# This code creates a dictionary variable named "student" student = # This line opens a file named "student.txt" in write mode (w) file = open("student.txt", "w") # This line converts the "student" dictionary to a string using the str() function and writes it to the file file.write(str(student)) # This line closes the "student.txt" file file.close()
The above code creates a dictionary variable named “student” and then opens a file named “student.txt” in write mode (w).
Then, it converts the “student” dictionary to a string using the str() function and writes it to the file using the file.write(str(student)) statement.
Finally, the file.close() function is used to close the file after the data is written.
You may also like to read the following Python tutorials.
In this tutorial, we learned about how to Python write variable to file and covered the below methods:
Using the repr() function
Using the pickle.dump() function
Using the string formatting
Using the str() function
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First line: bobby Second line: hadz Third line: com
Formatted string literals (f-strings) let us include expressions inside of a string by prefixing the string with f .
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var1 ='bobby' var2 ='hadz' result =f'var1>var2>'print(result)# 👉️ bobbyhadz
Make sure to wrap expressions in curly braces - .
# Using a for loop to write a list of strings to a file on new lines
Use a for loop if you need to write a list of strings to a file on a new line every time.
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withopen('example.txt','w', encoding='utf-8')as my_file: a_list =['bobby','hadz','com']for item in a_list: my_file.write(f'item>\n')
We used a for loop to iterate over the list, added a newline character to the end of each item and wrote the result to a file.
# Defining a reusable function
If you have to do this often, define a reusable function.
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defwrite_on_separate_lines(file_name, lines):withopen(file_name,'w', encoding='utf-8')asfile:for line in lines:file.write(f'line>\n') write_on_separate_lines('example.txt',['bobby','hadz','com'])
The function takes a file name and a list of lines as parameters and writes the lines to the file, appending a newline character at the end of each line.
# Write a string to a file on a new line every time using join()
You can also use the str.join() method to write a string to a file on a new line every time.
The code sample writes the strings to the file on new lines, however, we have to manually close the file after we're done.
This is an issue because if an error is raised before the file.close() line runs, we would get a memory leak.
On the other hand, the with open() statement takes care of automatically closing the file even if an error is raised.
Calling the file.write() method without using the with statement or calling file.close() might result in the arguments of file.write() not being completely written to the disk.
The newer with open() syntax is a much better option and should be your preferred approach.
# Additional Resources
You can learn more about the related topics by checking out the following tutorials:
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Count number of unique Words in a String or File in Python
Create a file name using Variables in Python
How to generate unique IDs or File Names in Python
How to get the File path of a Class in Python
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