Nil*_*age 6 python dataframe pandas
我有一个像下面这样的单词列表.
wordlist = ['p1','p2','p3','p4','p5','p6','p7']
数据框如下所示.
df = pd.DataFrame({'id' : [1,2,3,4],
'path' : ["p1,p2,p3,p4","p1,p2,p1","p1,p5,p5,p7","p1,p2,p3,p3"]})
Run Code Online (Sandbox Code Playgroud)
输出:
id path
1 p1,p2,p3,p4
2 p1,p2,p1
3 p1,p5,p5,p7
4 p1,p2,p3,p3
Run Code Online (Sandbox Code Playgroud)
我想计算路径数据以获得以下输出.是否有可能实现这种转变?
id p1 p2 p3 p4 p5 p6 p7
1 1 1 1 1 0 0 0
2 2 1 0 0 0 0 0
3 1 0 0 0 2 0 1
4 1 1 2 0 0 0 0
Run Code Online (Sandbox Code Playgroud)
您可以使用矢量化字符串方法str.count()
(请参阅文档和参考),并将wordlist中的每个元素提供给新数据帧:
In [4]: pd.DataFrame({name : df["path"].str.count(name) for name in wordlist})
Out[4]:
p1 p2 p3 p4 p5 p6 p7
id
1 1 1 1 1 0 0 0
2 2 1 0 0 0 0 0
3 1 0 0 0 2 0 1
4 1 1 2 0 0 0 0
Run Code Online (Sandbox Code Playgroud)
更新:评论的一些答案.实际上,如果字符串可以是彼此的子串,这将不起作用(但OP应该澄清它).如果是这种情况,这将起作用(并且也更快):
splitted = df["path"].str.split(",")
pd.DataFrame({name : splitted.apply(lambda x: x.count(name)) for name in wordlist})
Run Code Online (Sandbox Code Playgroud)
还有一些测试可以支持我更快的声明:-)
当然,我不知道实际用例是什么,但是我把数据框放大了一点(只重复了1000次,差异就大了) :
In [37]: %%timeit
....: splitted = df["path"].str.split(",")
....: pd.DataFrame({name : splitted.apply(lambda x: x.count(name)) for name i
n wordlist})
....:
100 loops, best of 3: 17.9 ms per loop
In [38]: %%timeit
....: pd.DataFrame({name:df["path"].str.count(name) for name in wordlist})
....:
10 loops, best of 3: 23.6 ms per loop
In [39]: %%timeit
....: c = df["path"].str.split(',').apply(Counter)
....: pd.DataFrame({n: c.apply(lambda x: x.get(n, 0)) for n in wordlist})
....:
10 loops, best of 3: 42.3 ms per loop
In [40]: %%timeit
....: dfN = df["path"].str.split(',').apply(lambda x: pd.Series(Counter(x)))
....: pd.DataFrame(dfN, columns=wordlist).fillna(0)
....:
1 loops, best of 3: 715 ms per loop
Run Code Online (Sandbox Code Playgroud)
我也用更多的元素进行了测试wordlist
,结论是:如果你有一个更大的数据帧,wordlist
我的方法中元素数量相对较少,如果你有一个很大wordlist
的方法,Counter
来自@RomanPekar可以更快(但只有最后一个).
我认为这会很有效率
# create Series with dictionaries
>>> from collections import Counter
>>> c = df["path"].str.split(',').apply(Counter)
>>> c
0 {u'p2': 1, u'p3': 1, u'p1': 1, u'p4': 1}
1 {u'p2': 1, u'p1': 2}
2 {u'p1': 1, u'p7': 1, u'p5': 2}
3 {u'p2': 1, u'p3': 2, u'p1': 1}
# create DataFrame
>>> pd.DataFrame({n: c.apply(lambda x: x.get(n, 0)) for n in wordlist})
p1 p2 p3 p4 p5 p6 p7
0 1 1 1 1 0 0 0
1 2 1 0 0 0 0 0
2 1 0 0 0 2 0 1
3 1 1 2 0 0 0 0
Run Code Online (Sandbox Code Playgroud)
另一种方法:
>>> dfN = df["path"].str.split(',').apply(lambda x: pd.Series(Counter(x)))
>>> pd.DataFrame(dfN, columns=wordlist).fillna(0)
p1 p2 p3 p4 p5 p6 p7
0 1 1 1 1 0 0 0
1 2 1 0 0 0 0 0
2 1 0 0 0 2 0 1
3 1 1 2 0 0 0 0
Run Code Online (Sandbox Code Playgroud)
一些粗略的性能测试:
>>> dfL = pd.concat([df]*100)
>>> timeit('c = dfL["path"].str.split(",").apply(Counter); d = pd.DataFrame({n: c.apply(lambda x: x.get(n, 0)) for n in wordlist})', 'from __main__ import dfL, wordlist; import pandas as pd; from collections import Counter', number=100)
0.7363274283027295
>>> timeit('splitted = dfL["path"].str.split(","); d = pd.DataFrame({name : splitted.apply(lambda x: x.count(name)) for name in wordlist})', 'from __main__ import dfL, wordlist; import pandas as pd', number=100)
0.5305424618886718
# now let's make wordlist larger
>>> wordlist = wordlist + list(lowercase) + list(uppercase)
>>> timeit('c = dfL["path"].str.split(",").apply(Counter); d = pd.DataFrame({n: c.apply(lambda x: x.get(n, 0)) for n in wordlist})', 'from __main__ import dfL, wordlist; import pandas as pd; from collections import Counter', number=100)
1.765344003293876
>>> timeit('splitted = dfL["path"].str.split(","); d = pd.DataFrame({name : splitted.apply(lambda x: x.count(name)) for name in wordlist})', 'from __main__ import dfL, wordlist; import pandas as pd', number=100)
2.33328927599905
Run Code Online (Sandbox Code Playgroud)
看完这个话题后我发现这Counter
很慢.您可以使用defaultdict
以下方法优化它:
>>> def create_dict(x):
... d = defaultdict(int)
... for c in x:
... d[c] += 1
... return d
>>> c = df["path"].str.split(",").apply(create_dict)
>>> pd.DataFrame({n: c.apply(lambda x: x[n]) for n in wordlist})
p1 p2 p3 p4 p5 p6 p7
0 1 1 1 1 0 0 0
1 2 1 0 0 0 0 0
2 1 0 0 0 2 0 1
3 1 1 2 0 0 0 0
Run Code Online (Sandbox Code Playgroud)
和一些测试:
>>> timeit('c = dfL["path"].str.split(",").apply(create_dict); d = pd.DataFrame({n: c.apply(lambda x: x[n]) for n in wordlist})', 'from __main__ import dfL, wordlist, create_dict; import pandas as pd; from collections import defaultdict', number=100)
0.45942801555111146
# now let's make wordlist larger
>>> wordlist = wordlist + list(lowercase) + list(uppercase)
>>> timeit('c = dfL["path"].str.split(",").apply(create_dict); d = pd.DataFrame({n: c.apply(lambda x: x[n]) for n in wordlist})', 'from __main__ import dfL, wordlist, create_dict; import pandas as pd; from collections import defaultdict', number=100)
1.5798653213942089
Run Code Online (Sandbox Code Playgroud)