擅长:python、mysql、java
<p>我试着应用你的答案,但并没有得到很好的结果,正如你在下面看到的:我只是得到了相同的值1970-01-01,而不是在datetime列中存储了具有相同值的列。到达列为空,而不是根据需要(从df1)计算到达次数</p>
<pre><code>df3 = pandas.merge(df1,df2_gr, left_on='datetime', right_on ='Datain',how='left').fillna(0)
df3
category datetime arrivals departures occupancy dayofweek Arrival category
0 pat 2013-01-01 0 0 0 1 1970-01-01 0
1 pat 2013-01-02 0 0 0 2 1970-01-01 0
2 pat 2013-01-03 0 0 0 3 1970-01-01 0
3 pat 2013-01-04 0 0 0 4 1970-01-01 0
4 pat 2013-01-05 0 0 0 5 1970-01-01 0
5 pat 2013-01-06 0 0 0 6 1970-01-01 0
6 pat 2013-01-07 0 0 0 0 1970-01-01 0
7 pat 2013-01-08 0 0 0 1 1970-01-01 0
8 pat 2013-01-09 0 0 0 2 1970-01-01 0
</code></pre>