2

我有以下列表和数据框：

mylist = ['foo', 'bar', 'baz']
df = pd.DataFrame({'Col1': ['fooThese', 'barWords', 'baz are', 'FOO: not', 'bAr:- needed'],
                   'Col2': ['Baz:Neither', 'Foo Are', 'barThese', np.nan, 'but this is fine']})

如果在 DataFrame 中找到，我想替换 mylist 中的字符串。我可以使用以下正则表达式模式替换一些：

pat = '|'.join([r'\b{}'.format(w) for w in mylist])
df2 = df.replace(pat, '', regex=True)

但是，这并没有放置所有实例。我想要的输出如下：

    Col1     Col2
0   These    Neither
1   Words    Are
2   are      These
3   not      NaN
4   needed   but this is fine
4

2 回答 2

5

您必须使用?i使您的替换不区分大小写的正则表达式标志，还要删除特殊字符：

mydict = {f'(?i){word}': '' for word in mylist}
df2 = df.replace(mydict, regex=True).replace('[:-]', '', regex=True)

      Col1              Col2
0    These           Neither
1    Words               Are
2      are             These
3      not               NaN
4   needed  but this is fine

或者您可以将特殊字符添加到您的字典中，这样您就不必调用DataFrame.replace两次：

mydict = {f'(?i){word}': '' for word in mylist}#.update({'[:-]': ''})
mydict['[:-]'] = ''
df2 = df.replace(mydict, regex=True)

      Col1              Col2
0    These           Neither
1    Words               Are
2      are             These
3      not               NaN
4   needed  but this is fine
于 2020-04-04T17:55:21.933 回答
0

另一种解决方案

使用Pandas Seriestr.replace()方法

import pandas as pd
mylist = ['foo', 'bar', 'baz']
df = pd.DataFrame({'Col1': ['fooThese', 'barWords', 'baz are', 'FOO: not', 'bAr:- needed'],
                   'Col2': ['Baz:Neither', 'Foo Are', 'barThese', np.nan, 'but this is fine']})

def replace_str_in_df_with_list(df, list, subst_string):
    """ Function which replaces strings in a DataFrame based on a list of strings.

    Parameters:
    ----------
    df :  <pd.DataFrame> instance
        The input DataFrame on which to perform the substitution.
    list : list
        The list of strings to use for the substitution.
    subst_string : str
        The substitution string.

    Returns:
    -------
    new_df : <pd.DataFrame> instance
        A new DataFrame with strings replaced.

    """
    df_new = df.copy()
    subst_string = str(subst_string)
    # iterate over each columns as a pd.Series() to use that method
    for c in df_new:
        # iterate over the element of the list
        for elem in list:
            df_new[c] = df_new[c].str.replace(elem, subst_string, case=False)

    return(df_new)

df2 = replace_str_in_df_with_list(df, mylist, '')

不幸的是，这种方法在DataFrame（还没有？）上不可用。

这里提供的解决方案并不完美，但它并没有在应用函数之前修改输入列表。


更多帮助：

https://pandas.pydata.org/pandas-docs/stable/search.html?q=replace

于 2020-04-04T18:27:47.467 回答