[英]How to replace a part of a string in a pandas.Dataframe?
I am trying to replace a part of all strings in pd.Dataframe, but it doe s not work. 我试图替换pd.Dataframe中所有字符串的一部分,但它不起作用。
My data example: 我的数据示例:
HLAA0101
HLAA0201
HLAA0202
HLAA0203
HLAA0205
What am I trying to obtain: 我想要获得什么:
A0101
A0201
A0202
A0203
A0205
My code: 我的代码:
mhc = train_csv.mhc
for i in mhc:
i[0:2].replace('HLA', ' ')
print(mhc)
But it does not work. 但它不起作用。
Option 1: 选项1:
df['mhc'] = df['mhc'].str[3:]
Option 2: 选项2:
df['mhc'] = df['mhc'].str.replace(r'^HLA','')
Option 3: 选项3:
df['mhc'] = df['mhc'].str.extract(r'HLA(.*)', expand=False)
Option 4: (NOTE: sometimes list comprehension works faster than internal vectorized methods for string/object dtypes) 选项4 :(注意:有时列表理解比字符串/对象dtypes的内部向量化方法更快)
df['mhc'] = [s[3:] for s in df['mhc']]
All options yield the same result: 所有选项都会产生相同的结果:
In [26]: df
Out[26]:
mhc
0 A0101
1 A0201
2 A0202
3 A0203
4 A0205
Timing for 50.000 rows DF: 时间为50.000行DF:
In [29]: df = pd.concat([df] * 10**4, ignore_index=True)
In [30]: %timeit df['mhc'].str[3:]
35.9 ms ± 3.18 ms per loop (mean ± std. dev. of 7 runs, 10 loops each)
In [31]: %timeit df['mhc'].str.replace(r'^HLA','')
162 ms ± 3.04 ms per loop (mean ± std. dev. of 7 runs, 10 loops each)
In [32]: %timeit df['mhc'].str.extract(r'HLA(.*)', expand=False)
164 ms ± 4.87 ms per loop (mean ± std. dev. of 7 runs, 10 loops each)
In [33]: %timeit [s[3:] for s in df['mhc']]
14.6 ms ± 18.6 µs per loop (mean ± std. dev. of 7 runs, 100 loops each)
In [34]: df.shape
Out[34]: (50000, 1)
Conclusion: list comprehension approach won. 结论:列表理解方法获胜。
Use - 使用 -
mhc = mhc.str.replace('HLA', ' ')
OR - 要么 -
train_csv['mhc'] = train_csv['mhc'].str.replace('HLA', '') # One liner directly from df
Try str.replace
. 试试
str.replace
。 (Documentation here: https://pandas.pydata.org/pandas-docs/stable/generated/pandas.Series.str.replace.html ) (此处的文档: https : //pandas.pydata.org/pandas-docs/stable/generated/pandas.Series.str.replace.html )
Also, in your code it inserts a space instead of the replaced strings. 此外,在您的代码中,它插入一个空格而不是替换的字符串。 If you want that, that's fine, otherwise delete the space.
如果你想要,那很好,否则删除空格。 ;)
;)
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