![]() ![]() To return selected elements of a generator, you can use itertools.islice. A generator yields items instead of returning a list.Īn example of Fibonacci generator: def fibonacci_generator(b=1): In Python, a generator is a function that behaves like an iterator. I wrote this code for a fibonacci sequence generator ![]() Int, float, str, tuple, frozenset, bytes, already provided a nice review, I will focus on the generator part. Here's an overview of mutable and immutable types in Python: Mutable objects: This will assign a new empty list as a default value to sequence_list every time the function is called, instead of once at compile time. To def this_behaves_as_expected(my_list=None): The recommended way is to switch from def this_can_go_wrong_easily(my_list=): ![]() Produces Initialization, added 0 and starting number 1 to sequence listĬurrent position: 0, Total values: 1 calculating next value Produces Initialization, added 0 and starting number 10 to sequence listĬurrent position: 1, Total values: 2 calculating next value Go ahead and try this out for yourself, here is one example: fibonacci_calc(10, 0, 3) The problems will only become appearant once you call the function multiple times during one execution. I personally haven't encountered such use cases, but there might be some. You should only ever do that if you have a good reason for it and know exactly what you're doing. I have made this mistake before and the bugs it produced were incredibly hard to fix before I knew what I was looking for. You are using an empty list as the default value sequence_list in your function header: def fibonacci_calc(current_val, current_pos=0, max_seq_length=5, sequence_list=): Using a mutable type as a default argument is generally not a good idea. Python Mutable Defaults Are The Source of All Evil Those messages are likely superfluous for other purposes. I'm assuming all the print statements are just debugging aids and wouldn't be included in the final version. Here's an example of a function that addresses my concerns: def get_fibonacci_sequence(start_num, seq_length):įibonacci_seq.append(fibonacci_seq + fibonacci_seq) Here, you would likely be better off just logging a message instead of introducing more overhead by using an exception. Raise Exception("Please initalize with 0".format(fibonacci_calc._name_, fibonacci_calc._code_.co_varnames)) If(current_pos != 0 and len(sequence_list) = 0): Can anyone tell me whether my code is designed well? if not, why? import loggingĭef fibonacci_calc(current_val, current_pos=0, max_seq_length=5, sequence_list=): ) and any generator is also an iterable.I wrote this code for a fibonacci sequence generator. An iterable is anything you can iterate (e.g. The next function is the built-in function that requests the next value from the iterable. Here is a quick self-explanationary example: > def example(): ![]() As the generator stops, it won’t hang up despite that loop. As you see in the definition of fibGenerator above, there is a endless while-loop which has a yield inside. Using a generator allows you to create an endless sequence. The next time you request a value, the generator will continue where it left off. A yield will “return” a value and pause the generator. You create a generator by simply using yield instead of return. The values are generated lazily, that means when you request it. Still not too sure what the generator does however.Ī generator is a Python function which generates a sequence of return values. Instead of iterating over a range and calling next on the generator manually, you then can also just use the take-recipe from itertools to do it just like this: fibonaccinumbers = take(20, fibGenerator()) You can also use a generator function to make that all easier: def fibGenerator(): That way you don’t have to do the same things over and over again. You should define it outside of it and just reuse it.Īlso, when you know you want to create a list of multiple fibonacci numbers, it helps to just store all the numbers you calculate in between. Then you are redefinining your fib function inside the loop over and over again. Also, you can simplify the whole block by just doing this: numberlist = list(range(20))Īnd given that you don’t actually need that to be a list, you don’t need to construct that at all but you can just run for n in range(20) later. You don’t need to initialize i there, the for loop does that for you. Also some more comments on your code: numberlist = ![]()
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