python之用字典实现代换， map 函数

 

用字典实现代换

 

# 创建字典, 数据框中的值为 key， 用 value 替换

map_dic = {'key1':'value1', 'key2':'value2'}
df['column_name'] = df['column_name'].map(map_dic)


# 下面是将一列的元素编序号做键值对, 可忽略
map_dic = {}
i = 0
for r in df['column_name']:
    if r not in map_dic:
        map_dic[r] = i
        i += 1