I have a line of code like this:
list1=[string1[i:i+int1] for i in range(0, len(string1), int1)] I remember my teacher saying that we should start new lines when there is 'for' so, is there a way to write this code that looks like:
for i in range(0, len(string1), int1): #something here or something else?
You mean to extract a boring old regular for loop from a list-comprehension?
list1=[string1[i:i+int1] for i in range(0, len(string1), int1)] Becomes:
list1 = list() for i in range(0, len(string1), int1): list1.append(string1[i:i+int1]) This would be useful if you wanted to add exception handling, logging, or more complex functions or behaviors while you iterate over your data.
For instance:
list1 = list() for i in range(0, len(string1), int1): log.info('in loop: i={}'.format(i)) try: data = string1[i:i+int1] except: log.error('oh no!') # maybe do something complex here to get some data anyway? data = complex_function(i) log.debug('appending to list: data={}'.format(data)) list1.append(data) But generally speaking the list-comprehension is a totally legitimate way to write that.
[somefunction(val) for val in values]. Assuming that was appropriate for the case, of course. As another potentially appropriate alternative, rather than returning a list, one could yield data and get a generator out of the deal.
list, though ideally, they wouldn't do that in the first place. :-) That said, the incremental cost of list() over [] is pretty small, about 60-70 extra ns on my machine (admittedly an increase of 2-3.5x over the base cost of [] of ~20-30 ns, but unlikely to matter in all but the hottest of loops).
something = [] is more immediately recognisable than something = list() to me.You have to create the empty list first, and then append for each iteration.
list1 = [] for i in range(0, len(string1), int1): list1.append(string1[i:i+int1]) That list comprehension would translate to:
l = [] for i in range(0, len(string1), int1): l.append(string1[i:i+int1]) Little bit dirty, but a good alternative for splitting collection to subcollections of a fixed size.
from itertools import zip_longest l = [] for chunk in zip_longest(*([iter(string1)]*int1), fillvalue=''): l.append(''.join(chunk)) 
g = (string[i:i+int1] for i,char in enumerate(string) if i % int1 == 0) l = list(g) Do not use len(iterable) in the while dealing with indices. Use enumerate() for that. It yields (index, item). This is efficient and pythonic.
The idea that you should make a newline while using for loop is probably idiomatic to some other language, C, C++ e.g. But not in python. List comprehensions come fro the Haskell world of FP. So that's elegant as they come.
forinside of an expression isn't part of a for statement; it's part of a list comprehension.forloops that build alistpiecemeal. If they did, they aren't really teaching you Python.