Python 将字符串的数据帧列合并到Pandas中的单个列中
我在数据框(从CSV导入)中有包含如下文本的列Python 将字符串的数据帧列合并到Pandas中的单个列中,python,pandas,Python,Pandas,我在数据框(从CSV导入)中有包含如下文本的列 "New york", "Atlanta", "Mumbai" "Beijing", "Paris", "Budapest" "Brussels", "Oslo", "Singapore" 我想将所有列折叠/合并为一列,如下所示 New york Atlanta Beijing Paris Budapest Brussels Oslo Singapore 如何在pandas中执行此操作?假设您有这样一个数据帧: >>> df
"New york", "Atlanta", "Mumbai"
"Beijing", "Paris", "Budapest"
"Brussels", "Oslo", "Singapore"
我想将所有列折叠/合并为一列,如下所示
New york Atlanta
Beijing Paris Budapest
Brussels Oslo Singapore
如何在pandas中执行此操作?假设您有这样一个
数据帧:
>>> df
0 1 2
0 New york Atlanta Mumbai
1 Beijing Paris Budapest
2 Brussels Oslo Singapore
然后,简单使用pd.DataFrame.apply
方法将很好地工作:
>>> df.apply(" ".join, axis=1)
0 New york Atlanta Mumbai
1 Beijing Paris Budapest
2 Brussels Oslo Singapore
dtype: object
注意,我必须传递axis=1,以便它跨列应用,而不是跨行应用。即:
>>> df.apply(" ".join, axis=0)
0 New york Beijing Brussels
1 Atlanta Paris Oslo
2 Mumbai Budapest Singapore
dtype: object
更快(但更丑)的版本包括:
在较大(10kx5)数据帧上:
%timeit df.apply(" ".join, axis=1)
10 loops, best of 3: 112 ms per loop
%timeit df[0].str.cat(df.ix[:, 1:].T.values, sep=' ')
100 loops, best of 3: 4.48 ms per loop
A B C result
0 New york Beijing Brussels New york Beijing Brussels
1 Atlanta Paris Oslo Atlanta Paris Oslo
2 Mumbai Budapest Singapore Mumbai Budapest Singapore
以下是更多的方法:
def pir(df):
df = df.copy()
df.insert(2, 's', ' ', 1)
df.insert(1, 's', ' ', 1)
return df.sum(1)
def pir2(df):
df = df.copy()
return pd.MultiIndex.from_arrays(df.values.T).to_series().str.join(' ').reset_index(drop=True)
def pir3(df):
a = df.values[:, 0].copy()
for j in range(1, df.shape[1]):
a += ' ' + df.values[:, j]
return pd.Series(a)
时机
pir3似乎比小型df
pir3在较大的df
30000行上仍然最快
为了完整起见:
In [160]: df1.add([' '] * (df1.columns.size - 1) + ['']).sum(axis=1)
Out[160]:
0 New york Atlanta Mumbai
1 Beijing Paris Budapest
2 Brussels Oslo Singapore
dtype: object
说明:
In [162]: [' '] * (df.columns.size - 1) + ['']
Out[162]: [' ', ' ', '']
针对300K行DF的计时:
In [68]: df = pd.concat([df] * 10**5, ignore_index=True)
In [69]: df.shape
Out[69]: (300000, 3)
In [76]: %timeit df.apply(" ".join, axis=1)
1 loop, best of 3: 5.8 s per loop
In [77]: %timeit df[0].str.cat(df.ix[:, 1:].T.values, sep=' ')
10 loops, best of 3: 138 ms per loop
In [79]: %timeit pir(df)
1 loop, best of 3: 499 ms per loop
In [80]: %timeit pir2(df)
10 loops, best of 3: 174 ms per loop
In [81]: %timeit pir3(df)
10 loops, best of 3: 115 ms per loop
In [159]: %timeit df.add([' '] * (df.columns.size - 1) + ['']).sum(axis=1)
1 loop, best of 3: 478 ms per loop
结论:如果您喜欢更明确的内容,当前的赢家是
从如下所示的数据帧df开始:
>>> df
A B C
0 New york Beijing Brussels
1 Atlanta Paris Oslo
2 Mumbai Budapest Singapore
df['result'] = df['A'] + ' ' + df['B'] + ' ' + df['C']
可以创建如下所示的新列:
>>> df
A B C
0 New york Beijing Brussels
1 Atlanta Paris Oslo
2 Mumbai Budapest Singapore
df['result'] = df['A'] + ' ' + df['B'] + ' ' + df['C']
在这种情况下,结果存储在原始数据帧的“结果”列中:
%timeit df.apply(" ".join, axis=1)
10 loops, best of 3: 112 ms per loop
%timeit df[0].str.cat(df.ix[:, 1:].T.values, sep=' ')
100 loops, best of 3: 4.48 ms per loop
A B C result
0 New york Beijing Brussels New york Beijing Brussels
1 Atlanta Paris Oslo Atlanta Paris Oslo
2 Mumbai Budapest Singapore Mumbai Budapest Singapore
您可以通过df.T.apply(“.join”)来保存一些字符。
挑剔:pir3
应该连接df.values[:,0]
,df.values[:,1]
。@juanpa.arrivillaga您的意思是什么<代码>局部放电浓度
?或np.连接
?这两个都不能组合字符串。我必须使用join
。除非我误解了你的意思。我指的是+
操作员。反正你现在已经修好了。