splitting lines, need to add element of same kind

[Serafim]

Without any assumption about the number of different animals in the file maybe something like this.

from datetime import datetime
 
now = datetime.now()
date_time = now.strftime("%m/%d/%Y")
to_app ='C:/02/All_an.txt'
 
animals = dict()

with open (to_app, 'r+') as app:
    for ln_in_file in app :
        ln_in_file=ln_in_file.strip()

        line, P, num, animal = ln_in_file.split(',')
        if animal in animals:
            animals[animal]['count'] += int(num)
        else:
            animals[animal] = {'count': int(num), 'P': P, 'date': date_time}

for animal in animals:    
    print(f"{animals[animal]['date']},{animals[animal]['count']},{animals[animal]['P']},{animal}")

As I don't know anything about the function of 'P' and 'lineNN', I omitted the 'lineNN' and replaced it with the date, but kept the rest. If this is not necessary, the code can be much simplified:

from datetime import datetime
 
now = datetime.now()
date_time = now.strftime("%m/%d/%Y")
to_app ='C:/02/All_an.txt'
 
animals = dict()

with open (to_app, 'r+') as app:
    for ln_in_file in app :
        ln_in_file=ln_in_file.strip()

        line, P, num, animal = ln_in_file.split(',')
        if animal in animals:
            animals[animal] += int(num)
        else:
            animals[animal] = int(num)

for animal, count in animals.items():
    print(f"{date_time},{count},P,{animal}")