是否可以将我的代码转换为列表理解？ 我该如何改进我的代码？

Question

Is it possible to turn the part of my code where there is a nested for loop into a list comprehension? also how can i improve my code. What it does is takes a input and displays all the permutations/combos

N = "123123"
s = []
def combos():
    global s
    for i in range(len(N)):
        for j in range(i+1,len(N) + 1):
            s.append(N[i:j])
    s = list(set(s)) # converting to set to remove duplication


combos()

Answer 1

Yes, it should be possible to turn this function to a list comprehension. I used the itertools module for this (it's my first time using it, so it may not look "correct" to people more experiencied with it).

However, do you really want all the permutations? Because I'm don't think this is what your function currently does.

Anyways, here's what you could do using itertools.permutations :

s = list(set(["".join(i) for j in range(len(N)+1) for i in itertools.permutations(N, j)]))

Warning : it doesn't output the same result as your function.

Note: you can also try replacing itertools.permutations by itertools.combinations as I'm not quite sure of what you want. The syntax is exactly the same, you literally just have to replace "permutations" by "combinations".

Output for itertools.permutations :

271 substrings - ['', '231132', '122133', '1232', '23131','3', '312123', '131232', '313122', '123', '332', '223311','332211', '1321', '233121', '322113', '23123', '313221', '113223', '212133', '313', '2313', '3311', '311322', '321231', '22131', '2311', '31212', '1323', '1123', '32131', '3221', '32312', '211233', '21233', '321123', '32231', '13321', '323112', '31', '132', '2121', '122', '13122', '1', '232', '121233', '312312', '311232', '213321', '13123', '322131', '1313', '22133', '32112', '231213', '332112', '233211', '123321', '133', '1322', '123312', '132132', '21331', '3123', '131223', '21313', '133221', '21', '3211', '31322', '32213', '32321', '22113', '312132', '1312', '33112', '12231', '22311', '233112', '132123', '13221', '21321', '1213', '12312',
 '13', '1331', '2321', '221133', '23113', '3312', '31232','213132', '23321', '123132', '3322', '122331', '12', '3231', '12331', '321132', '32113', '21132', '323211', '3213', '33122', '113', '13213', '2123', '213', '12133', '21312', '312', '31221', '121323', '331212', '32132', '3121', '13223','223', '1212', '31312', '132321', '3212', '33211', '1223','133212', '221313', '113232', '121332', '231', '131', '12123', '132231', '213213', '121', '321', '33', '33121', '223131', '31231', '123213', '321321', '321312', '231321', '21133', '312321', '322', '11', '2133', '33212', '313212', '331122', '232131', '11232', '21213', '23121', '1233', '3113', '112233', '13322', '23311', '31213', '212331', '323121', '213231', '31321', '11332', '21323', '22331', '31223', '221331', '2312', '1332', '2231', '221', '1132', '23', '1133', '113
23', '2323', '3321', '231123', '1221', '2332', '331', '12233', '23112', '33221', '213123', '23132', '11233', '2233', '323', '312231', '32311', '32123', '211332', '113322', '231312', '132213', '212313', '11322', '223113', '2331', '2', '211', '23231', '332121', '3232', '23213', '322311', '12132', '2113', '233', '23312', '31122', '32121', '12332', '3122', '232311', '13232', '331221', '132312', '13132', '112', '12321', '231231', '3112', '3131', '212', '13212', '2112', '13312', '232113', '1122', '112323', '2132', '3223', '123123', '21231', '31132', '1231', '2211', '23211', '32', '21123','2131', '123231', '321213', '133122', '122313', '112332', '22', '12313', '2213', '131322', '3132', '13231', '311223','12213', '12323', '21332', '31123', '32211', '213312', '312213', '11223', '311', '22313', '211323']