diff --git a/exercises/practice/robot-name/.approaches/introduction.md b/exercises/practice/robot-name/.approaches/introduction.md index c4b6738380..d0140e6534 100644 --- a/exercises/practice/robot-name/.approaches/introduction.md +++ b/exercises/practice/robot-name/.approaches/introduction.md @@ -1,12 +1,15 @@ # Introduction -Robot Name in Python is an interesting exercise for practising randomness. + +Robot Name in Python is an interesting exercise for practicing randomness. ## General Guidance -Two ways immedietely come to mind: generate all the possible names and then return them sequentially, or generate a random name and ensure that it's not been previously used. + +Two ways immediately come to mind: generate all the possible names and then return them sequentially, or generate a random name and ensure that it has not been previously used. Randomness can be a little, well, random, so **it's very easy to have an incorrect solution and still pass the tests**. It's strongly recommended to submit your solution for Code Review. ## Approach: mass name generation + We'd first have to generate all the possible names, shuffle them, and then use `next` (the simplest way) or maintain a `current_index` and get the name. Here's a possible way to do it: @@ -26,14 +29,17 @@ class Robot(object): def reset(self): self.name = next(NAMES) ``` + Note that selecting randomly from the list of all names would be incorrect, as there's a possibility of the name being repeated. For more detail and explanation of the code, [read here][approach-mass-name-generation]. ## Approach: name on the fly -Another approach is to generate the name on the fly and add it to a cache or a store, and checking if the generated name hasn't been used previously. + +Another approach is to generate the name on the fly and add it to a cache or a store, checking if the generated name hasn't been used previously. A possible way to implement this: + ```python from string import ascii_uppercase, digits from random import choices diff --git a/exercises/practice/robot-name/.approaches/mass-name-generation/content.md b/exercises/practice/robot-name/.approaches/mass-name-generation/content.md index 392a34ca19..a245195fa5 100644 --- a/exercises/practice/robot-name/.approaches/mass-name-generation/content.md +++ b/exercises/practice/robot-name/.approaches/mass-name-generation/content.md @@ -1,8 +1,9 @@ # Mass Name Generation -We'd first have to generate all the possible names, shuffle them, and then use `next` (the simplest way) or maintain a `current_index` and get the name. -Note that selecting randomly from the list of all names would be incorrect, as there's a possibility of the name being repeated. -Here's a possible way to do it: +We first generate all the possible names, shuffle them, and then either use `next` (the simplest way) or maintain a `current_index` to get the name. +Note that selecting randomly from the list of all names would be incorrect, as there is a possibility of the name being repeated. + +One possible way to do it: ```python from itertools import product @@ -25,25 +26,27 @@ class Robot(object): The first few lines of the mass name generation uses [`itertools.product`][itertools-product]. The resultant code is a simplification of: + ```python letter_pairs = (''.join((l1, l2)) for l1 in ascii_uppercase for l2 in ascii_uppercase) numbers = (str(i).zfill(3) for i in range(1000)) names = [l + n for l in letter_pairs for n in numbers] ``` -After the name generation, the names are shuffled - using the [default `seed`][random-seed] in the `random` module (the current timestamp). +After the name generation, the names are shuffled - using the [default `seed`][random-seed] in the `random` module (the current timestamp). When the tests reseed `random`, this has no effect as the names were shuffled before that. -We then set `NAMES` to the iterable of names, and in `reset`, set the robot's name to the `next(name)`. -If you'd like, read more on [`iter` and `next`][iter-and-next]. +We then set `NAMES` to the iterable of names, and in `reset`, set the robot's name to the `next(name)`. +If you are interested, you can read more on [`iter` and `next`][iter-and-next]. -Unlike the on the fly approach, this has a relatively short "generation" time, because we're merely giving the `next` name instead of generating it. -However, this has a huge startup memory and time cost, as 676,000 strings have to be calculated and stored. +Unlike the [on the fly approach][approach-name-on-the-fly], this has a relatively short "generation" time, because we are merely giving the `next` name instead of generating it. +However, this has a huge startup memory and time cost, as 676,000 strings have to be calculated and stored. For an approximate calculation, 676,000 strings * 5 characters / string * 1 byte / character gives 3380000 bytes or 3.38 MB of RAM - and that's just the memory aspect of it. -Sounds small, but it's relatively very expensive at the beginning. +Sounds small, but this might be a relatively significant startup cost. Thus, this approach is inefficient in cases where only a small number of names are needed _and_ the time to set/reset the robot isn't crucial. [random-seed]: https://docs.python.org/3/library/random.html#random.seed [iter-and-next]: https://www.programiz.com/python-programming/methods/built-in/iter [itertools-product]: https://www.hackerrank.com/challenges/itertools-product/problem +[approach-name-on-the-fly]: https://exercism.org/tracks/python/exercises/robot-name/approaches/name-on-the-fly diff --git a/exercises/practice/robot-name/.approaches/name-on-the-fly/content.md b/exercises/practice/robot-name/.approaches/name-on-the-fly/content.md index 0aa9f9a3fa..494b32b2d1 100644 --- a/exercises/practice/robot-name/.approaches/name-on-the-fly/content.md +++ b/exercises/practice/robot-name/.approaches/name-on-the-fly/content.md @@ -1,7 +1,9 @@ # Find name on the fly -We generate the name on the fly and add it to a cache or a store, and checking if the generated name hasn't been used previously. + +We generate the name on the fly and add it to a cache or a store, checking to make sure that the generated name has not been used previously. A possible way to implement this: + ```python from string import ascii_uppercase, digits from random import choices @@ -10,7 +12,7 @@ cache = set() class Robot: - def __get_name(self): + def __get_name(self): return ''.join(choices(ascii_uppercase, k=2) + choices(digits, k=3)) def reset(self): @@ -19,18 +21,30 @@ class Robot: cache.add(name) self.name = name - def __init__(self): + def __init__(self): self.reset() ``` -We use a `set` for the cache as it has a low access time, and we don't need the preservation of order or the ability to be indexed. -This way is merely one of the many to generate the name. +We use a `set` for the cache as it has a low access time, and because we do not need the preservation of order or the ability to access by index. + +Using `choices` is one of the many ways to generate the name. Another way might be to use `randrange` along with `zfill` for the number part, and a double `random.choice` / `random.choice` on `itertools.product` to generate the letter part. -This is the shortest way, and best utilizes the Python standard library. +The first is shorter, and best utilizes the Python standard library. + +As we are using a `while` loop to check for the name generation, it is convenient to store the local `name` using the [walrus operator][walrus-operator]. +It's also possible to find the name once before the loop, and then find it again inside the loop, but that would be an unnecessary repetition: + +```python +def reset(self): + name = self.__get_name() + while name in cache: + name = self.__get_name() + cache.add(name) + self.name = name +``` -As we're using a `while` loop to check for the name generation, it's convenient to store the local `name` using the [walrus operator][walrus-operator]. -It's also possible to find the name before the loop and find it again inside the loop, but that would unnecessary repetition. A helper method ([private][private-helper-methods] in this case) makes your code cleaner, but it's equally valid to have the code in the loop itself: + ```python def reset(self): while (name := ''.join(choices(ascii_uppercase, k=2) + choices(digits, k=3))) in cache: @@ -39,14 +53,15 @@ def reset(self): self.name = name ``` -We call `reset` from `__init__` - it's syntactically valid to do it the other way round, but it's not considered good practice to call [dunder methods][dunder-methods] directly. +We call `reset` from `__init__` - it is syntactically valid to do it the other way around, but it is not considered good practice to call [dunder methods][dunder-methods] directly. This has almost no startup time and memory, apart from declaring an empty `set`. -Note that the _generation_ time is the same as the mass generation approach, as a similar method is used. +Note that the _generation_ time is the same as the [mass generation approach][approach-mass-name-generation], as a similar method is used. However, as the name is generated at the time of setting/resetting, the method time itself is higher. -In the long run, if many names are generated, this is inefficient, since collisions will start being generated more often than unique names. +In the long run, if many names are generated, this is inefficient, since collisions will start being generated more often than unique names. [walrus-operator]: https://realpython.com/python-walrus-operator/ [private-helper-methods]: https://www.geeksforgeeks.org/private-methods-in-python/ -[dunder-methods]: https://dbader.org/blog/python-dunder-methods \ No newline at end of file +[dunder-methods]: https://dbader.org/blog/python-dunder-methods +[approach-mass-name-generation]: https://exercism.org/tracks/python/exercises/robot-name/approaches/mass-name-generation