[英]Replace character of column value with string from another column in Pandas
name value_1
dd3 what, _ is
dd4 what, _ is
How to replace '_' from value_1 column with whole string from name column? 如何用名称列中的整个字符串替换value_1列中的'_'?
Desired output for value_1 column value_1列的所需输出
value_1
what, dd3 is
what, dd4 is
I have tried with this: 我已经尝试过:
df['value_1'] = df['value_1'].apply(lambda x:x.replace("_", df['name']))
And I got this error :expected a string or other character buffer object
我得到了这个
error :expected a string or other character buffer object
Use apply
with axis=1
for process by rows: 将
apply
with axis=1
用于按行处理:
df['value_1'] = df.apply(lambda x:x['value_1'].replace("_", x['name']), axis=1)
print (df)
name value_1
0 dd3 what, dd3 is
1 dd4 what, dd4 is
UPDATE: similar to @jezrael's solution, but it should be bit faster for larger data sets (vectorized approach): 更新:类似于@jezrael的解决方案,但对于较大的数据集(矢量化方法)应该更快一些:
In [221]: df['value_1'] = (df.groupby('name')['value_1']
.transform(lambda x: x.str.replace('_', x.name)))
In [222]: df
Out[222]:
name value_1
0 dd3 what, dd3 is
1 dd4 what, dd4 is
Old answer: 旧答案:
you can create a helper DF: 您可以创建一个帮助DF:
In [181]: x = df.value_1.str.split('_', expand=True)
In [192]: x
Out[192]:
0 1
0 what, is
1 what, is
then insert a new column into it: 然后在其中插入新列:
In [182]: x.insert(1, 'name', df['name'])
which yields: 产生:
In [194]: x
Out[194]:
0 name 1
0 what, dd3 is
1 what, dd4 is
and replace the original column: 并替换原始列:
In [183]: df['value_1'] = x.sum(1)
In [184]: df
Out[184]:
name value_1
0 dd3 what, dd3 is
1 dd4 what, dd4 is
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