print(): Print Objects To File Function

The Python print function is used to output data to a file. If no file is specified then the data will be ouput to the standard output. The print function accepts a variable number of strings, to print more than one string simply pass the strings to the print function in a comma separated fashion, see example 2.

Below is the function prototype for the print function.

print(objects, sep=' ', end='\n', file=None, flush=False)

In the python file below we make a single call to the print function to output the string Hello World!.

#!/usr/bin/python3

def main():
    print("Hello World!")

if __name__ == "__main__":
    main()

Now we can run the Python file and observe the string Hello World! being printed to /dev/stdout.

user-1@vm:~/Documents$ ./print_example_1.py
Hello World!
user-1@vm:~/Documents$ 

In the Python file below we are making a single call to the print function, however this time we are passing multiple comma separated unnamed arguments to the print function.

#!/usr/bin/python3

def main():
    student_1 = "John"
    student_2 = "Alex"
    student_3 = "Anthony"

    print(student_1, student_2, student_3)

if __name__ == "__main__":
    main()

Now we can run the Python file on the command line and observe how the three names are printed to /dev/stdout.

user-1@vm:~/Documents$ ./print_example_2.py
John Alex Anthony
user-1@vm:~/Documents$ 

This example demonstrates the use of the sep keyword argument to specify a custom separator. The separator is the string which is printed between each object that is passed to the print function. The default value of sep is a single space character ' '. In the example below sep is assigned the string ', ' (a comma followed by a space).

#!/usr/bin/python3

def main():
    student_1 = "John"
    student_2 = "Alex"
    student_3 = "Anthony"

    print(student_1, student_2, student_3, sep=", ")

if __name__ == "__main__":
    main()

Now let's run this python program in a terminal and observe the output.

user-1@vm:~/Documents$ ./python_example_3.py
John, Alex, Anthony
user-1@vm:~/Documents$ 

As you can see, the print function now outputs a comma and a space between each name.

Objects may define a __str__ method which should return a string object and will be called when an attempt is made to get the string value of an object. When an object is passed to the print function each objects __str__ method is called. Thus you may control how your objects get printed by writing a __str__ method for those objects.

In the example below we define a __str__ method which returns the name of the object when called.

#!/usr/bin/python3

class Fruit:
    def __init__(self, name):
        self.name = name

    def __str__(self):
        return self.name

def main():
    my_favorite_fruit = Fruit("orange")
    not_a_real_fruit = Fruit("tomato")
    print(my_favorite_fruit, not_a_real_fruit)

if __name__ == "__main__":
    main()

And when we run the program we can see that orange tomato is the string that gets printed.

user-1@vm:~/Documents$ ./python_example_4.py
orange tomato
user-1@vm:~/Documents$