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[英]In Python/Pandas, what is the most efficient way, to apply a custom function, to a column of a dataframe, where the input includes strings?
[英]What is the most efficient method to apply a function to a column in a dask dataframe?
我有一个 function 可以标记元组中的单词:
def get_word_tokens(tokens):
words = [token[0] for token in tokens]
return words
我想将此应用于 dask dataframe 中的列并创建一个新列,例如
df1
#phrase tokens
0 call CHRIS MOBILE. [(call, 0, 4),
(CHRIS, 5, 10),
(MOBILE, 11, 17)]
1 call Tod Sarks [(call, 0, 4),
(Tod, 5, 8),
(arks, 9, 14)]
创建列词
df1
#phrase tokens words
0 call CHRIS MOBILE. [(call, 0, 4), call, CHRIS, MOBILE
(CHRIS, 5, 10),
(MOBILE, 11, 17)]
1 call Tod Sarks [(call, 0, 4), call, Tod, Sarks
(Tod, 5, 8),
(Sarks, 9, 14)]
我努力了:
df['words'] = df.apply(lambda row: get_word_tokens(df['tokens']), axis = 1)
这似乎有效,但需要很长时间才能运行? 有没有更快的方法?
您将df['tokens']
传递给 function,这是完整的列。 这应该有效:
def get_word_tokens(tokens):
words = [token[0] for token in tokens]
return words
data = [
['call CHRIS MOBILE.', [('call', 0, 4),
('CHRIS', 5, 10),
('MOBILE', 11, 17)]],
['call Tod Sarks', [('call', 0, 4),
('Tod', 5, 8),
('arks', 9, 14)]],
]
import pandas as pd
df = pd.DataFrame(data, columns=['phrase', 'tokens'])
df = pd.concat([df,df,df,df, df, df])
import dask.dataframe as dd
ddf = dd.from_pandas(df, npartitions=2)
def get_word_tokens_df(df):
df['words'] = df['tokens'].apply(get_word_tokens)
return df
ddf = ddf.map_partitions(get_word_tokens_df)
ddf.compute()
尝试这个:
df.join(df['tokens'].str.extractall(r'([A-Za-z]\w+)').groupby(level=0).agg(','.join).squeeze().rename('words'))
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