Loop like a native: while, for, iterators, generators

What people said

Strong rec Marwan Mostafa · 2019-06 · Stack Overflow · on “Difference between Python's Generators and Iterators”

Examples from Ned Batchelder [this video] highly recommended for iterators and generators A method without generators that do something to even numbers def evens(stream): them = [] for n in stream: if n % 2 == 0: them.append(n) return them while by using a generator def evens(stream): for n in stream: if n % 2 == 0: yield n We don't need any list nor a return statement Efficient for large/ infinite length stream ... it just walks and yield the value Calling the evens method (generator) is as usual num = [...] for n in evens(num): do_smth(n) Generator also used to Break double loop Iterator A book full of pages is an iterable , A bookmark is an iterator and this bookmark has nothing to do except t

Recommends JaminSore · 2013-08 · Stack Overflow · on “Scipy minimize, fmin, leastsq type problems (setting array element with sequence), bad fit”

No problem. To convert your function to a scalar, simple `return (result**2).sum()`. Also, `for i in range(len(x))` is almost always unnecessary as is looping over lists of numpy arrays. Your problem could probably be greatly simplified and sped up using numpy's broadcasting rules [LINK] . If you find you *have* to loop over lists of arrays, have a look at this video [this video] for a more Pythonic approach.

Recommends Back2Basics · 2013-11 · Stack Overflow · on “"Can only iterable" Python error”

An iterable is a thing with multiple items that you can iterate through (for example: take the 1st value do something, then the 2nd do something, etc...) Lists, dictionaries, tuples, strings have several items in them and can be used as iterables. As a counterexample: number types don't qualify as iterable. Remember that computers count from #0 so: if you want the first value of a list you can use my_list[0] before you go further I would suggest watching this video about looping. [this video]

Recommends SylvainD · 2016-01 · Code Review Stack Exchange · on “Game of Life search program for Herschel-generating baits”

Iterations The pythonic way to iterate is to use the for keyword, usually without bothering about indices. I suggest you have a look at the presentation : Ned Batchelder: Loop like a native: while, for, iterators, generators (PyCon US) ( video on Youtube [this video] / text with slides [LINK] ). In your case, most loops can be rewritten. For instance : n = 0 while n < testrect[2]: m = 0 while m < testrect[3]: o = 0 while o < len(stillLifes): testReaction(n + testrect[0], m + testrect[1], o) o += 1 m += 1 n += 1 could be written : for n in range(testrect[2]) for m in range(testrect[3]): for o, _ in enumerate(stillLifes): testReaction(n + testrect[0], m + testrect[1], o) Also, the for loop accepts

Recommends alexwlchan · 2016-10 · Code Review Stack Exchange · on “List of all prime factors of a number, including repeats”

Some general comments: Hooray for docstrings! It’s great that you’re writing these – it makes your code much easier to read and review, because I know what it’s supposed to do (and so can judge whether it does it correctly). And in general, these are pretty good docstrings. Do note that PEP 257 [LINK] says that one-line docstrings should end in a period. Don’t be stingy with variable names – characters are cheap, and if you write more descriptive names, the code becomes much easier to follow. For example, in generate_primes() , known_primes is better than l . There are a few minor PEP 8 [LINK] violations – in particular, space after comma in function arguments ( for i in range(1,n+1) ) and a

Recommends Back2Basics · 2016-11 · Stack Overflow · on “Python use command word in the function”

Command would be rewritten from this command = command[1:] command = command[:-1] command = command[15:] to this: command[16:-1] if you want to split up a string by a comma letter use: my_list = command.split(',') I think practicing with these 2 concepts will help you in your programming. (Python is not like C). Watch this for more looping details [this video]

Recommends Kevin J. Chase · 2017-03 · Stack Overflow · on “Using iter function inside next function”

`for index in range(len(anything)):` is a mistake most of the time --- Python will do all that busywork for you. Your loop could be as simple as `for char in string: print char`. See Ned Batchelder's " Loop Like a Native [LINK] " (30-minute video from PyCon US 2013 [this video] ) for easy ("Pythonic") ways to handle many cases like this.

Recommends diek · 2017-10 · Stack Overflow · on “string comparison for multiple values python”

Watch this, it will help a lot. Ned Batchelder - Loop like a native: while, for, iterators, generators [this video]

Recommends skrx · 2017-11 · Stack Overflow · on “Combining selected items from different lists into a new one”

You're welcome. BTW, I recommend watching Ned Batchelder's presentation "Loop like a native: while, for, iterators, generators" [this video] .

Recommends Post169 · 2018-03 · Stack Overflow · on “How can I break out of multiple loops?”

Yes, a speaker at a PyCon claims here [this video] that even @RobertRossney's accepted answer is not truly Pythonic, but a generator is the right way to break multiple loops. (I'd recommend watching the whole video!)