Assume you have some function function in Python that works by looping: for example it could be a function that evaluates a certain mathematical expression, e.g. x**2, for all elements from an array, e.g. ([1, 2, ..., 100]) (obviously this is a toy example). Would it be possible to write a code such that, each time function goes through a loop and obtains a result, some code is executed, e.g. print("Loop %s has been executed" % i)? So, in our example, when x**1 has been computed, the program prints Loop 1 has been executed, then when x**2 has been computed, it prints Loop 2 has been executed, and so on.
Note that the difficulty comes from the fact that I do not program the function, it is a preexisting function from some package (more specifically, the function I am interested in would be GridSearchCV from package scikit learn).
The easiest way to do this would be to just copy the function's code into your own function, tweak it, and then use it. In your case, you would have to subclass GridSearchCV and override the _fit method. The problem with this approach is that it may not survive a package upgrade.
In your case, that's not necessary. You can just specify a verbosity level when creating the object:
GridSearchCV(verbose=100)
I'm not entirely sure what the verbosity number itself means. Here's the documentation from the package used internally that does the printing:
The verbosity level: if non zero, progress messages are printed. Above 50, the output is sent to stdout. The frequency of the messages increases with the verbosity level. If it more than 10, all iterations are reported.
You can look at the source code if you really want to know what the verbosity number does. I can't tell.