The print function

I've been taking it for granted so far that the Python shell automatically prints the result of any statement that is entered. However, if you want to see the result of a particular operation inside a Python program, you will need to explicitly print it using the print() function. To use the print() function, you can type print() with the value that you would like to print inside parentheses.

Here are some examples using the print() function:

or example:>> print(0)
>> print(1+1)
>> print('abc')
>> print("abc" == "cba")

The syntax used with the print function may seem a bit strange right now, but it will become more clear when I introduce functions later in the chapter. 

There are two areas that the print() function comes in handy. The first of these is to test and debug programs. In order to see whether your program is working properly, or why it is not working properly, it is helpful to look inside the program while it is running. You can do this by placing print() functions in the program where you want to investigate what is happening. To give a really basic example, if a program that outputs a number produces the wrong number, one approach is to print the number at various stages of the program to identify where things go wrong. 

The second use of print() functions is to track the progress or status of a program. Processing large datasets can often take a really long time, so it can be helpful to have some sense of how far along the program is and how long it might take to finish. For example, when processing a large dataset row by row, it can be helpful to print out the fraction of rows that have been processed.