嵌套if条件以在pandas datafram中创建新列

Question

我有一个如下所示的数据帧：

|userid|rank2017|rank2018|
|212   |'H'     |'H'     |    
|322   |'L'     |'H      |
|311   |'H'     |'L'     |

我想在上面的dataframe中创建一个名为progress的新列，如果rank2017等于rank2018，它将输出1；如果rank2017是'H'，rank2018是'L'，否则输出2。有人能帮我用python执行这个吗

Answer 1

以下是使用np.select的方法：

# Set your conditions:
conds = [(df['rank2017'] == df['rank2018']), 
         (df['rank2017'] == 'H') & (df['rank2018'] == 'L')]

# Set the values for each conditions
choices = [1, 2]

# Use np.select with a default of 3 (your "else" value)    
df['progress'] = np.select(conds, choices, default = 3)

退货：

^{pr2}$

Answer 2

有一种方法。不需要使用嵌套的if语句。在

df = pd.DataFrame({'user': [212, 322, 311],
                   'rank2017': ['H', 'L', 'H'],
                   'rank2018': ['H', 'H', 'L']})

df['progress'] = 3
df.loc[(df['rank2017'] == 'L') & (df['rank2018'] == 'H'), 'progress'] = 2
df.loc[df['rank2017'] == df['rank2018'], 'progress'] = 1

#   rank2017 rank2018  user  progress
# 0        H        H   212         1
# 1        L        H   322         2
# 2        H        L   311         3