时间戳减法必须具有相同的时区或没有时区，但它们都是 UTC

Question

有一些问题可以解决相同的错误，TypeError: Timestamp subtraction must have the same timezones or no timezones但没有一个问题会遇到与此相同的问题。

我有 2 个 UTC 时间戳，在减去时会抛出该错误。

print(date, type(date), date.tzinfo)
>>> 2020-07-17 00:00:00+00:00 <class 'pandas._libs.tslibs.timestamps.Timestamp'> UTC
print(date2, type(date2), date2.tzinfo)
>>> 2020-04-06 00:00:00.000000001+00:00 <class 'pandas._libs.tslibs.timestamps.Timestamp'> UTC
date - date2
>>> TypeError: Timestamp subtraction must have the same timezones or no timezones

编辑：我使用的是Python 3.6.9和Pandas 1.0.1

Answer 1

检查时区类型后：type(date.tzinfo)给出<class 'datetime.timezone'>并type(date2.tzinfo)给出<class 'pytz.UTC'>，因此根据 pandas 源代码，即使它们都是 UTC，它们也不被认为是相等的。

所以解决方案是让它们具有相同的tzinfo类型（pytz或datitme.timezone）

这是 Github 中的一个未决问题：https ://github.com/pandas-dev/pandas/issues/32619

Answer 2

有同样的问题。如果您使用 pandas 读取数据read_csv，它将使用<class 'pytz.UTC'>. 所以我的解决方案是在任何地方简单地使用相同的类。

示例代码生成错误

from datetime import datetime, timedelta, timezone
import pandas as pd

now = datetime.now(tz=timezone.utc)
some_time_ago = now - timedelta(7)

print('Timezone info before reading_csv')
print(some_time_ago.tzinfo, type(some_time_ago.tzinfo))

time_passed = now - some_time_ago
print (time_passed)

df = pd.DataFrame([some_time_ago], columns=['date'])
df.to_csv('dates.csv', index=False)

df2 = pd.read_csv('dates.csv', parse_dates=['date'])
print('\nTimezone info after reading_csv')
print(df2.iloc[0,0].tzinfo, type(df2.iloc[0,0].tzinfo))

now = datetime.now(tz=timezone.utc)
some_time_ago = now - df2.iloc[0,0]
print(some_time_ago)

Timezone info before reading_csv
UTC <class 'datetime.timezone'>
7 days, 0:00:00

Timezone info after reading_csv
UTC <class 'pytz.UTC'>
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-23-b2815e32e8b7> in <module>
     19 
     20 now = datetime.now(tz=timezone.utc)
---> 21 some_time_ago = now - df2.iloc[0,0]
     22 print(some_time_ago)

pandas/_libs/tslibs/c_timestamp.pyx in pandas._libs.tslibs.c_timestamp._Timestamp.__sub__()

TypeError: Timestamp subtraction must have the same timezones or no timezones

使用 pytz 正确代码

import pytz
from datetime import datetime, timedelta
import pandas as pd

now = datetime.now(tz=pytz.UTC)
some_time_ago = now - timedelta(7)

print('Timezone info before reading_csv')
print(some_time_ago.tzinfo, type(some_time_ago.tzinfo))

time_passed = now - some_time_ago
print (time_passed)

df = pd.DataFrame([some_time_ago], columns=['date'])
df.to_csv('dates.csv', index=False)

df2 = pd.read_csv('dates.csv', parse_dates=['date'])
print('\nTimezone info after reading_csv')
print(df2.iloc[0,0].tzinfo, type(df2.iloc[0,0].tzinfo))

now = datetime.now(tz=pytz.UTC)
some_time_ago = now - df2.iloc[0,0]
print(some_time_ago)

Timezone info before reading_csv
UTC <class 'pytz.UTC'>
7 days, 0:00:00

Timezone info after reading_csv
UTC <class 'pytz.UTC'>
7 days 00:00:00.024021