Having a custom function in a snippet that you can quickly grab and paste into the code, and then use to debug, can be very useful. If you're fast, you can always code one on the fly. The important thing is to code it in a way that it won't leave stuff around when you eventually remove the calls and its definition. Therefore it's important to code it in a way that is completely self-contained. Another good reason for this requirement is that it will avoid potential name clashes with the rest of the code.

Let's see an example of such a function:

# custom.py
def debug(*msg, print_separator=True):
    print(*msg)
    if print_separator:
        print('-' * 40)

debug('Data is ...')
debug('Different', 'Strings', 'Are not a problem')
debug('After while loop', print_separator=False)

In this case, I am using a keyword-only argument to be able to print a separator, which is a line of 40 dashes.

The function is very simple. I just redirect whatever is in msg to a call to print and, if print_separator is True, I print a line separator. Running the code will show the following:

$ python custom.py
Data is ...
----------------------------------------
Different Strings Are not a problem
----------------------------------------
After while loop

As you can see, there is no separator after the last line.

This is just one easy way to somehow augment a simple call to the print function. Let's see how we can calculate a time difference between calls, using one of Python's tricky features to our advantage:

# custom_timestamp.py
from time import sleep

def debug(*msg, timestamp=[None]):
    print(*msg)
    from time import time  # local import
    if timestamp[0] is None:
        timestamp[0] = time()  #1
    else:
        now = time()
        print(
            ' Time elapsed: {:.3f}s'.format(now - timestamp[0])
        )
        timestamp[0] = now  #2

debug('Entering nasty piece of code...')
sleep(.3)
debug('First step done.')
sleep(.5)
debug('Second step done.')

This is a bit trickier, but still quite simple. First, notice we import the time function from the time module from inside the debug function. This allows us to avoid having to add that import outside of the function, and maybe forget it there.

Take a look at how I defined timestamp. It's a list, of course, but what's important here is that it is a mutable object. This means that it will be set up when Python parses the function and it will retain its value throughout different calls. Therefore, if we put a timestamp in it after each call, we can keep track of time without having to use an external global variable. I borrowed this trick from my studies on closures, a technique that I encourage you to read about because it's very interesting.

Right, so, after having printed whatever message we had to print and some importing time, we then inspect the content of the only item in timestamp. If it is None, we have no previous reference, therefore we set the value to the current time (#1).

On the other hand, if we have a previous reference, we can calculate a difference (which we nicely format to three decimal digits) and then we finally put the current time again in timestamp (#2). It's a nice trick, isn't it?

Running this code shows this result:

$ python custom_timestamp.py
Entering nasty piece of code...
First step done.
 Time elapsed: 0.304s
Second step done.
 Time elapsed: 0.505s

Whatever your situation, having a self-contained function like this can be very useful.