如何比较datetime64[ns]的两个日期并选择最新的日期

除了序列对象的比较外,您选择的方法几乎很好。如果用x代替df\u analisis\u invertido,它应该可以工作。

举个例子:

import pandas as pd

data = {'t_first_conv':  [5, 21, 233],
    't_creation': [3, 23, 234],
    }

df = pd.DataFrame(data)
df['t_first_conv'] = pd.to_datetime(df['t_first_conv'])
df['t_creation'] = pd.to_datetime(df['t_creation'])
print(df)

# Change entry of first conversion column in case it is older/smaller than creation value (timestamps)
# Expected: 
# 0: 5     3
# 1: 23    23
# 2: 234   234

df['t_first_conv']=df.apply(lambda x: x['t_creation'] if x['t_first_conv'] < x['t_creation'] else x['t_first_conv'], axis=1)

print(df)