想要在 python 中出现某个任务名称的第一个日期

Question

I have an excel table that reads:

Task Name	End Date	Process ID
TASK 1	1st feb	65461
TASK 2	2nd feb	65461
TASK 1	3rd feb	65461

and i have a code that matches the ID and takes in the date for task 1 but I want to take the first end date for that task in python. Below is my code: '''

import pandas as pd
import numpy as np
df1 = pd.read_excel("Purchase Requisition and Purchase Order Approval Workflow Tasks.xlsx")
p_id,tk,ed =df1['Process ID'].tolist(),df1['Task Name'].tolist(),df1['End Date'].tolist()
ed = pd.to_datetime(df1['End Date'])
a = len(p_id)
x=np.array(p_id)
x=np.unique(p_id)
b=len(x)
inrfqdate=[None]*b
for i in range(0,b):
    for j in range(0,a):        
        if x[i] == p_id[j]:              
            if ("Initiate Purchase Requisition" in tk[j]):
                inrfqdate[i] = ed[j]

''' This takes the end date for latest task name appearing. I jut want it to store the first task date.

Answer 1

Here's a DataFrame I created to test my solution.

import pandas as pd

# Test Data Frame
data = {'Task Name': ['TASK 1', 'TASK 2', 'TASK 1', 'TASK 1', 'TASK 2', 'TASK 2'],
        'End Date': ['2/1/2021', '2/2/2021', '2/3/2021', '2/7/2021', '2/8/2021', 
                     '2/10/2021'],
        'Process ID': ['64561', '64561', '64561', '64562', '64562', '64562'],
    }

df = pd.DataFrame(data)

That gave me the following table:

Then I changed the dtype in the End Date column from an Object to a DateTime and added an additional column to find the Min Date grouped by Process ID and Task Name

# Convert Date Column from Object to DateTime
df['End Date'] = pd.to_datetime(df['End Date'])

# Create a 'Min Date' column and groupby parameters to select minimum date
df['Min Date'] = df.groupby(['Process ID', 'Task Name'])['End Date'].transform('min')

That gave me the following output:

You could also replace the current data in End Date by using:

df['End Date'] = df.groupby(['Process ID', 'Task Name'])['End Date'].transform('min')