有没有更有效的方法将映射应用于熊猫系列？

Question

我的 Pandas DataFrame 中有一个名为“State”的列。它包含美国州的缩写。我有硬编码的地区，我想为每个州的地区创建一个新列。我使用了 pd.Series.apply()，但我想知道这种类型的映射是否有更好的做法。关于如何改进我的代码的任何建议？这是我当前有效的代码，但我只是愿意就最佳实践提出建议。def get_region(s, *regions):    if s in regions[0]:        return 'west'    elif s in regions[1]:        return 'midwest'    elif s in regions[2]:        return 'south'    elif s in regions[3]:        return 'northeast'    else:        return Nonewest = ['WA','OR','CA','ID','NV','MT','WY','UT','AZ','CO','NM']midwest = ['ND','MN','WI','MI','SD','NE','KS','IA','MO','IL','IN','OH']south = ['TX','OK','AR','LA','MS','TN','KY','AL','GA','FL','SC','NC','VA','WV','MD','DE']northeast = ['PA','NJ','NY','CT','MA','RI','VT','NH','ME']regions = [west,midwest,south,northeast]full_df['Region'] = full_df['State'].apply(get_region, args=regions)full_df['Region'].head(15)Out:0          west1       midwest2         south3         south4       midwest5          west6         south7         south8          west9       midwest10        south11    northeast12    northeast13         west14         westName: Region, dtype: object

Answer 1

检查 map

s=pd.DataFrame([west,midwest,south,northeast],index=['west','midwest','south','northeast'])

s=s.reset_index().melt('index')

full_df['Region'] = full_df['State'].map(dict(zip(s['value'],s['index'])))

Answer 2

您可以尝试创建一个 dict 并将其映射到列：

west_dict = {i:"west" for i in west}

midwest_dict = {i:"midwest" for i in midwest}

south_dict = {i:"south" for i in south}

northeast_dict = {i:"northeast" for i in northeast}

d = {**west_dict, **midwest_dict, **south_dict, **northeast_dict}

full_df['Region'] = full_df['State'].map(d)