在python中将int转换为日期

Question

i have the following column

day
20190101
20190101
20190102
20190103

I want to change it to 01-01-2019 .

I used the following code for that

data['day'] = pd.to_datetime(data['day'], format='%Y/%m/%d')

but it gives the following output instead: 1970-01-01 00:00:00.020190101

data[["day"]] = data[["day"]].apply(pd.to_datetime)

also tried

data['day'] = pd.to_datetime(data['day'], format='%Y/%m/%d')

expected output is 01-01-2019 but the actual output is 1970-01-01 00:00:00.020190101

Answer 1

You can simply implement:

def func(val):
    x = str(val)
    return '{}-{}-{}'.format(x[6:8],x[4:6],x[0:4])

And then run it for each entry.

Answer 2

Just fix the format argument of to_datetime function, you have %Y/%m/%d while the actual format is %Y%m%d :

df['dt'] = pd.to_datetime(df['day'], format='%Y%m%d')

print(df)

Output:

        day         dt
0  20190101 2019-01-01
1  20190101 2019-01-01
2  20190102 2019-01-02
3  20190103 2019-01-03