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python - python iloc错误新列数据框

问题描述

我有这个 python 脚本，这只是它的一部分，它可以工作，但只有 2 行我遇到了麻烦：

not_marketo.loc['Marketo DEP'] = "NO"
yes_marketo.loc[:,'Marketo DEP'] = C

我已经尝试了所有可能的方法：

not_marketo['Marketo DEP'] = "NO"
not_marketo.loc['Marketo DEP'] = "NO"
not_marketo.loc[:,'Marketo DEP'] = "NO"

“试图在 DataFrame 的切片副本上设置一个值。尝试改用 .loc[row_indexer,col_indexer] = value”

SettingWithCopyWarning：
pandas\core\indexing.py:1596：SettingWithCopyWarning：试图在 DataFrame 中的切片副本上设置值请参阅文档中的警告： https ://pandas.pydata.org/pandas-docs /stable/user_guide/indexing.html#returning-a-view-versus-a-copy iloc._setitem_with_indexer(indexer, value, self.name)

# Entry Point List (epl)
df_left = df_db[['Email', 'SOURCE', 'Data Entry Point', 'File']]
df_right = df_mto[['Email', 'Entry Point List', 'Marketo']]
df_epl = pd.merge(df_left, df_right, on="Email", how = 'outer')
df_epl.loc[df_epl['Marketo'].isnull(), 'Marketo'] = 'NO'
df_epl.loc[:,'Entry Point List'] = df_epl['Entry Point List'].str.replace('|',' ', regex=True)

# List of Data Entry Points from the Files
dep_list = df_epl[['Data Entry Point']]
dep_list = dep_list.dropna()
dep_list = dep_list.drop_duplicates()
list = dep_list['Data Entry Point'].tolist()

# By Groups
yes_marketo = df_epl[(df_epl['Marketo'] == "YES") & (df_epl['File'].notnull())]
not_marketo = df_epl[(df_epl['Marketo'] == "NO")  & (df_epl['File'].notnull())]
not_files   = df_epl.loc[df_epl['File'].isnull()]

# If not in Marketo not Entry Data Point
not_marketo.loc['Marketo DEP'] = "NO"

# Check Entry Point List for yes_marketo
C = []
for index, row in yes_marketo.iterrows():

    if row['Data Entry Point'] in row['Entry Point List']:
        C.append('YES')
    else:
        C.append('NO')

yes_marketo.loc[:,'Marketo DEP'] = C

标签： pythonpandasdataframepandas-loc

解决方案

您在显示的代码中多次不安全地对 DataFrame 进行了子集化：

# UNSAFE SUBSET HERE
dep_list = df_epl[['Data Entry Point']]

# UNSAFE SUBSET HERE
yes_marketo = df_epl[(df_epl['Marketo'] == "YES") & (df_epl['File'].notnull())]
# UNSAFE SUBSET HERE
not_marketo = df_epl[(df_epl['Marketo'] == "NO") & (df_epl['File'].notnull())]

# UNSAFE SUBSET HERE
not_files = df_epl.loc[df_epl['File'].isnull()]

可能最简单的修复方法是添加copy

dep_list = df_epl[['Data Entry Point']].copy()

yes_marketo = df_epl[
    (df_epl['Marketo'] == "YES") & (df_epl['File'].notnull())
    ].copy()

not_marketo = df_epl[
    (df_epl['Marketo'] == "NO") & (df_epl['File'].notnull())
    ].copy()

not_files = df_epl.loc[df_epl['File'].isnull()].copy()

这里有很多细节如何处理 Pandas 中的 SettingWithCopyWarning

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