Python Data Science Essentials - Third Edition

Iterators and generators

Looping through a list or a dictionary is very simple. Note that, with dictionaries, the iteration is key-based, which is demonstrated in the following example:

for entry in ['alpha', 'bravo', 'charlie', 'delta']:     print (entry) # prints the content of the list, one entry for line a_dict = {1: 'alpha', 2: 'bravo', 3: 'charlie', 4: 'delta'} for key in a_dict:     print (key, a_dict[key]) # Prints: # 1 alpha # 2 bravo # 3 charlie # 4 delta

On the other hand, if you need to iterate through a sequence and generate objects on the fly, you can use a generator. A great advantage of doing this is that you don't have to create and store the complete sequence at the beginning. Instead, you build every object every time the generator ...