python - 在时间序列中查找第一次出现

Question

I have a large dataframe with observations repeated each month.

I want to extract the first apparition of each observations.

For instance, consider the following dataset :

Name date          value 
A.   June 2020.     15
A.   July 2020.     20
A.   August 2020.   10
B.   July 2020.     30
B.   August 2020.   40
C.   August 2020.   5

I want to obtain :

Name date          value
A.   June 2020.     15
B.   July 2020.     30
C.   August 2020.   5

Answer 1

Lead function in SQL would be suitable. So you might be use sqlite or pandas in python. By using pandas, you could search "pandas lead" in google or stack, like this Pandas equivalent of Oracle Lead/Lag function .

Answer 2

你可以试试drop_duplicates

df.drop_duplicates(subset=['Name'], keep='first', inplace=True)