在 Pandas 数据帧中查找字符串模式匹配并返回匹配的字符串
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Find String Pattern Match in Pandas Dataframe and Return Matched Strin
提问by horatio1701d
I have a dataframe column with variable comma separated text and just trying to extract the values that are found based on another list. So my dataframe looks like this:
我有一个带有可变逗号分隔文本的数据框列，只是试图提取基于另一个列表找到的值。所以我的数据框看起来像这样：
col1 | col2
-----------
x | a,b
listformatch = [c,d,f,b]
pattern = '|'.join(listformatch)
def test_for_pattern(x):
if re.search(pattern, x):
return pattern
else:
return x
#also can use col2.str.contains(pattern) for same results
The above filtering works great but instead of returning bwhen it finds the match it returns the whole pattern such as a|binstead of just bwhereas I want to create another column with the pattern it finds such as b.
上面的过滤效果很好，但是b当它找到匹配项时不会返回，而是返回整个模式，a|b而不是仅仅返回，b而我想用它找到的模式创建另一列，例如b.
Here is my final function but still getting UserWarning: This pattern has match groups. To actually get the groups, use str.extract." groups, use str.extract.", UserWarning)I wish I can solve:
这是我的最终功能，但仍然UserWarning: This pattern has match groups. To actually get the groups, use str.extract." groups, use str.extract.", UserWarning)希望我能解决：
def matching_func(file1, file2):
file1 = pd.read_csv(fin)
file2 = pd.read_excel(fin1, 0, skiprows=1)
pattern = '|'.join(file1[col1].tolist())
file2['new_col'] = file2[col1].map(lambda x: re.search(pattern, x).group()\
if re.search(pattern, x) else None)
I think I understand how pandas extract works now but probably still rusty on regex. How do I create a pattern variable to use for the below example:
我想我现在了解Pandas提取物的工作原理，但在正则表达式上可能仍然生疏。如何创建用于以下示例的模式变量：
df[col1].str.extract('(word1|word2)')
Instead of having the words in the argument, I want to create variable as pattern = 'word1|word2'but that won't work because of the way the string is being created.
我不想在参数中包含单词，而是想创建变量 aspattern = 'word1|word2'但由于创建字符串的方式，这将不起作用。
My final and preferred version with vectorized string method in pandas 0.13:
我在 Pandas 0.13 中使用矢量化字符串方法的最终和首选版本：
Using values from one column to extract from a second column:
使用一列中的值从第二列中提取：
df[col1].str.extract('({})'.format('|'.join(df[col2]))
回答by Andy Hayden
You might like to use extract, or one of the other vectorised string methods:
您可能喜欢使用提取或其他矢量化字符串方法之一：
In [11]: s = pd.Series(['a', 'a,b'])
In [12]: s.str.extract('([cdfb])')
Out[12]:
0 NaN
1 b
dtype: object
