Question

我有这个代码块，它可以工作，但需要大约8秒才能执行。我知道它是第二个for循环，因为循环内部有一个循环。但是，我认为我需要两个循环，因为我需要交叉引用tracks列表。

有没有人知道如何让这个功能更快地执行？我似乎无法看到另一种写作方式。

仅供参考：我使用的csv文件有5570行，这是该函数采用＆＃34;而＃34;的另一个原因。

提前致谢！

def load_library(filename) :
    library = open(filename, 'rb')
    reader = csv.reader(library, delimiter = '|')
    tracks = set([])
    albums = set([])
    albums1 = set([])
    #albums1 is the set of albums which have already been added to the albums list.

    for row in reader : 
        artist, track, album, genre, year = row
        track = Track(artist, track)
        track.set_album(album)
        tracks.add(track)

    library = open(filename, 'rb')
    reader = csv.reader(library, delimiter = '|')

    for row in reader : 
        artist, track, album, genre, year = row
        a = Album(artist, album)
        for i in tracks :
            if str(i.album) == str(a.title) :
                a.add_track(i.title)
                if album not in albums1 :
                    albums.add(a)
        albums1.add(album)

    return tracks, albums

使用c.Profile后：

cProfile.run（＆＃39; load_library（）＆＃39;）                224565次函数调用9.776秒

   Ordered by: standard name

   ncalls  tottime  percall  cumtime  percall filename:lineno(function)
        1    0.002    0.002    9.776    9.776 <string>:1(<module>)
     5570    0.001    0.000    0.001    0.000 musiclib.py:18(set_album)
    11140    0.007    0.000    0.007    0.000 musiclib.py:23(__init__)
    92784    0.028    0.000    0.037    0.000 musiclib.py:31(add_track)
     5570    0.004    0.000    0.009    0.000 musiclib.py:6(__init__)
        1    9.723    9.723    9.775    9.775 musiclib.py:71(load_library)
        2    0.000    0.000    0.000    0.000 {_csv.reader}
    16710    0.002    0.000    0.002    0.000 {method 'add' of 'set' objects}
    92784    0.009    0.000    0.009    0.000 {method 'append' of 'list' objects}
        1    0.000    0.000    0.000    0.000 {method 'disable' of '_lsprof.Profiler' objects}
        2    0.000    0.000    0.000    0.000 {open}

Answer 1

只在一个for循环中执行此操作：

def load_library(filename) :
    library = open(filename, 'rb')
    reader = csv.reader(library, delimiter = '|')
    tracks = set([])
    albums = {}

    for row in reader : 
        artist, track, album, genre, year = row
        if album not in albums:
            a = Album(artist, album)
            albums[album] = a
        else:
            a = albums[album]
        a.add_track(track)
        track = Track(artist, track)
        track.set_album(album)
        tracks.add(track)
    return tracks, set(albums.values())

Python for loop效率

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