Python - simplifying code with list comprehension

Here you go:

[x['track'] for x in tempo_playlist if x['track'] in [y['track'] for y in energy_playlist]]

Although I agree with other people cramming in one line is less readable than multiple lines.

Does this help?

energy_tracks = [p["track"] for p in energy_playlist]
tempo_tracks = [p["track"] for p in tempo_playlist]

print set(energy_tracks).intersection(tempo_tracks)

Ok, in one line, you want it now :-D? I would ask why, but just for fun ...

result = set(p["track"] for p in energy_playlist).intersection(p["track"] for p in tempo_playlist)

Actually, this one-liner is maybe a bit faster than the three-liner above, as the lists of tracks are not explicitly saved in memory, but as iterators consumed by the set object.

Except that a) your code is more readable, so don't see the need of one line, but most importantly b) a one liner cannot improve really the performance :)... Let me demonstrate:

import timeit

energy_playlist = [{u'track': u'Nude', u'feature': u'energy', u'value': 0.342, u'artist': u'Radiohead'}, {u'track': u'Kaleidoscope', u'feature': u'energy', u'value': 0.285, u'artist': u'Coldplay'}, {u'track': u'Faust Arp', u'feature': u'energy', u'value': 0.289, u'artist': u'Radiohead'}, {u'track': u'Running Up That Hill', u'feature': u'energy', u'value': 0.356, u'artist': u'Placebo'}, {u'track': u'Codex', u'feature': u'energy', u'value': 0.128, u'artist': u'Radiohead'}, {u'track': u'True Love Waits', u'feature': u'energy', u'value': 0.132, u'artist': u'Radiohead'}, {u'track': u'Asleep - 2011 Remastered Version', u'feature': u'energy', u'value': 0.255, u'artist': u'The Smiths'}, {u'track': u'Glass Eyes', u'feature': u'energy', u'value': 0.11, u'artist': u'Radiohead'}, {u'track': u'Pyramid Song', u'feature': u'energy', u'value': 0.335, u'artist': u'Radiohead'}, {u'track': u'Life On Mars? - 2015 Remastered Version', u'feature': u'energy', u'value': 0.384, u'artist': u'David Bowie'}, {u'track': u'Exit Music (For a Film)', u'feature': u'energy', u'value': 0.276, u'artist': u'Radiohead'}, {u'track': u'Videotape', u'feature': u'energy', u'value': 0.384, u'artist': u'Radiohead'}, {u'track': u'High And Dry', u'feature': u'energy', u'value': 0.383, u'artist': u'Radiohead'}]
tempo_playlist = [{u'track': u'Codex', u'feature': u'tempo', u'value': 58.993, u'artist': u'Radiohead'}, {u'track': u'Pyramid Song', u'feature': u'tempo', u'value': 77.078, u'artist': u'Radiohead'}, {u'track': u'Videotape', u'feature': u'tempo', u'value': 77.412, u'artist': u'Radiohead'}]

def foo1():
    ret = []
    for d1 in energy_playlist:
        for d2 in tempo_playlist:
            if d1['track'] == d2['track']:
                ret.append(d1["track"])
    return ret

def foo2():
    ret = []
    for d1 in energy_playlist:
        for d2 in tempo_playlist:
            if d1['track'] == d2['track']:
                pass
    return None

def foo3():
    return [d2['track'] for d1 in energy_playlist for d2 in tempo_playlist if d1['track'] == d2['track']]


def bar():
    tempo_tracks = [i["track"] for i in tempo_playlist]
    return [i["track"] for i in energy_playlist if i["track"] in tempo_tracks]

print("foo1:", timeit.timeit(foo1))
print("foo2:", timeit.timeit(foo2))
print("foo3:", timeit.timeit(foo3))
print("bar:", timeit.timeit(bar))

# foo1: 5.550314342981437
# foo2: 5.025758317991858
# foo3: 5.3763819159939885
# bar: 2.86007208598312