如何使用 Pandas 检查一组值中的值顺序

Question

I have groups where I have the group name in the first column and the characteristcs in the second. If the order in the second is wrong, the third column should be set to NOT OK. How do I check if the order in each group is correct?

Answer 1

import pandas as pd

df = dict(num=['37671','37671','37671','37671','37671','37671','37671','37671','45559','45559','45559','45559','45559','45559','45559'],
         char=['No Characteristic','Primary','Secondary','Secondary','Secondary','Tertiary','Tertiary','Tertiary','No Characteristic','Secondary','Tertiary','Secondary','Secondary','Secondary','Tertiary'])
df = pd.DataFrame(df)
df

ordered_list = [pd.np.nan, 'No Characteristic','Primary','Secondary','Tertiary']

def check_in_list(row, ordered_list):
    status = 'NOT OK'
    char_idx = ordered_list.index(row['char'])
    char_prev_idx = ordered_list.index(row['char_prev'])
    if char_idx >= char_prev_idx:
        status = 'OK'
    return status

dfs = []
for num in df['num'].unique():
    df_ = df.loc[df['num'] == num, :]
    df_['char_prev'] = df_['char'].shift(1)
    df_['check'] = df_.apply(lambda row: check_in_list(row, ordered_list), axis=1)
    dfs.append(df_)
dfs = pd.concat(dfs)

dfs