将日期从序数编号转换为标准日期格式 - 熊猫

Question

我必须将日期列从整数/日期格式转换为日期格式d-m-y。示例：

import pandas as pd
col1 = [737346, 737346, 737346, 737346, 737059, 737346]
col2 = ['cod1', 'cod2', 'cod3', 'cod4', 'cod1', 'cod2']
dict = {'V1' : col1, 'V2' : col2}   
df = pd.DataFrame.from_dict(dict)
df
       V1    V2
0  737346  cod1
1  737346  cod2
2  737346  cod3
3  737346  cod4
4  737059  cod1
5  737346  cod2

预期：

df
           V1    V2
0  14-10-2019  cod1
1  14-10-2019  cod2
2  14-10-2019  cod3
3  14-10-2019  cod4
4  31-12-2018  cod1
5  14-10-2019  cod2

Answer 1

dateTime fromordinal应该有所帮助。

import datetime as dt
col1 = [737346, 737346, 737346, 737346, 737059, 737346]
col2 = ['cod1', 'cod2', 'cod3', 'cod4', 'cod1', 'cod2']
dd = {'V1' : col1, 'V2' : col2}   
df = pd.DataFrame.from_dict(dd)
df['V1'] = df['V1'].apply(dt.datetime.fromordinal)

Answer 2

只有 pandas Timestamp.fromordinal

df.V1.map(pd.Timestamp.fromordinal)
Out[511]: 
0   2019-10-14
1   2019-10-14
2   2019-10-14
3   2019-10-14
4   2018-12-31
5   2019-10-14
Name: V1, dtype: datetime64[ns]

Answer 3

您可以使用date.fromordinal。

from datetime import datetime as dt
df['V1'] = df.V1.apply(lambda x: dt.fromordinal(x)).dt.strftime('%d-%m-%Y')
print(df)
           V1    V2
0  14-10-2019  cod1
1  14-10-2019  cod2
2  14-10-2019  cod3
3  14-10-2019  cod4
4  31-12-2018  cod1
5  14-10-2019  cod2