how remove and print a specific item from a 2D array?

Question

I appear to be having this issue in my code and am unable to find a solution so I would be grateful if somebody could please have a look at lines 34,35 and 36 of my code to try and help me remove the required information from the array. (btw I apologise for the comment and general messiness within my code and the fact that it displayed n an external website but I was having issues with formatting on stack overflow)

thanks from Michael Roberts

print(" "*20,"Welcome to the greenfly population model") #printing intro
##########################declaing default variables#########################
generation_input = 10    #default number of generations
birthrate = 2            #default birthrate
juv = 10                 #default number of juveniles
adult = 10               #default number of adults
senile = 10              #default number of seniles
population=[]            # creating an empty list
population.append([juv,adult,senile]) #adding the default population values to the list
jsrate = 1               #default juvenile survival rate
asrate = 1               #default adult survival rate
ssrate = 0               #default senile survival rate

######################setting generation 0 values###################
def g0set():
    global generation_input,birthrate,jsrate,asrate,ssrate #declaring the variables globally
    generation_input = int(input("input number of generations for the model to run for:"))
    birthrate = float(input("input birthrate of model:"))
    juv = int(input("input number of juveniles in the model:"))
    adult = int(input("input number of adults in the model:"))
    senile = int(input("input number of seniles in the model:"))
    population.append([juv,senile,adult])           # adding the new population values into the list
    jsrate = float(input("input the juvenile survival rate of the model:"))
    asrate = float(input("input the adult survival rate of the model:"))
    ssrate = float(input("input the senile survival rate of the model:"))
    main_menu()

#####################displaying generation 0 values#################
def g0display():
    print("the model will run for ",generation_input," generations")
    print("the birthrate of the model is ", birthrate ) 
    print("the number of juveniles in the population model is ",population[0])
    print("the number of adults in the population model is ",population[1])
    print("the number of seniles in the population model is ",population[2])
    print("the juvenile survival rate is ",jsrate)
    print("the adult survival rate is ",asrate)
    print("the senile survival rate is ",ssrate)
    main_menu()



def run_program():
    global juv,adult,senile,generation_input,birthrate,jsrate,asrate,ssrate
    for i in range (0,generation_input): #looping round until it meets the required number of generations
        print (i+1) #printing which generation the loop is on(+1 as i starts from 0)
        print (population) #printing the array on which the population is stored
        juv1 = juv       #storing the previous juvenile values
        adult1 = adult   #storing the previous adult values
        senile1 = senile #storing the previous senile values
        juv= adult * birthrate #applying the birthrate to the adults to get the next generation of juveniles
        adult=juv1 #the previous generation's juveniles become adults
        senile=adult1 #the previous generation's adults become seniles
        juv1 = juv * jsrate #applying the juvenile survival rates with the next generation of juveniles to get the final number of next generation juveniles
        adult1 = adult * asrate #applying the juvenile survival rates with the next generation of adults to get the final number of next generation adults
        senile1 = senile * ssrate #applying the juvenile survival rates with the next generation of seniles to get the final number of next generation seniles
        population.append([juv1,adult1,senile1]) #adding the final values of the next generation to the population array
        juv=juv1 #setting the number of juveniles equal to that of the next generation
        adult=adult1 #setting the number of adults equal to that of the next generation
        senile=senile1 #setting the number of seniles equal to that of the next generation
    main_menu()    #returning to the menu after the program is finished

##################running the main menu#################
def main_menu():
    print("-"*35,"main menu","-"*34)    
    print("input 1 to set generation 0 values")     #printing possible options for the program
    print("input 2 to display generation 0 values") #printing possible options for the program
    print("input 3 to run the population model")    #printing possible options for the program
    choice = int(input()) 
    if choice == 1:
        g0set()
    elif choice == 2:
        g0display()
    elif choice == 3:
        run_program()
    else:
        print("incorrect value entered") 
        main_menu()


main_menu()

Answer 1

This

##########################declaing default variables#########################
population=[]            # creating an empty list
population.append([juv,adult,senile]) #adding the default population values 

creates a default setting, in

def g0set():
    global generation_input,birthrate,jsrate,asrate,ssrate #declaring the variables globally
    generation_input = int(input("input number of generations for the model to run for:"))
    birthrate = float(input("input birthrate of model:"))
    juv = int(input("input number of juveniles in the model:"))
    adult = int(input("input number of adults in the model:"))
    senile = int(input("input number of seniles in the model:"))
    population.append([juv,senile,adult])           # adding the new population values into the list
    jsrate = float(input("input the juvenile survival rate of the model:"))
    asrate = float(input("input the adult survival rate of the model:"))
    ssrate = float(input("input the senile survival rate of the model:"))
    main_menu()

You add the new settings on top, so now population looks like

[[10,10,10],[juv,senile,adult] # you flipped values of senile&adult here, by chance?

If you want to get a clean slate, do

population = [juv,adult,senile] # flipped to same order as earlier

in g0set() as well.

---

If you want to only print the last data in your population, use

print(population[-1][0]) # last elem of pop, print juv
print(population[-1][1]) # last elem op pop, print adult
print(population[-1][2]) # last elem of pop, print senile

---

The other thing that you should change is calling main_menue() on last line of every function: you are creating unnessesary function call stack frames.

Each time you call a function it places data on the stack, creates some space for its own variables etc (simplified) - you are diving ever deeper into the rabbithole. Its better to do it like so:

 while True:    # this will call until you leave your program with ctrl+c or your pc dies
    main_menu()

MainMenue changes to :

def main_menu():
    print("-"*35,"main menu","-"*34)    
    print("input 1 to set generation 0 values")     #printing possible options for the program
    print("input 2 to display generation 0 values") #printing possible options for the program
    print("input 3 to run the population model")    #printing possible options for the program
    choice = int(input()) 
    if choice == 1:
        g0set()
    elif choice == 2:
        g0display()
    elif choice == 3:
        run_program()
    else:
        print("incorrect value entered") 

And every other method also does no longer call main_menu() - it simply ends its job and then implicitly returns None to the main_menu(), it in turn returns None to the main body and the while True: will call your menu again.