help with python code

[imran akhtar]

A borough has made the following prognosis for the changes in population over the next few years:
• At the start of 2004 there were 26 000 inhabitants
• The rates of births and deaths are estimated at 0.7% and 0.6% of the population respectively
• The number of people moving in and out of the borough annually is estimated at 300 and 325 respectively.

i have to write a program that calculate the borough’s estimated population at the beginning of a particular year. The year in question should be requested from the user.

i have had, go, but does not seem to work. i would like help on how to start the code.

[bvdet]

Show us the work you have done so far, and we will try to help.

I think the calculation will go something like this:

population += population*(birth_rate - death_rate)
population += (movein_rate - moveout_rate)

This calculation will need to be done for each year in the difference between the target date and 2004.

I would create a function that returns the projected population.

def projected_pop(year):
    ....code....
    return calculated_pop

The input could be done something like this:

print int(projected_pop(int(raw_input("Enter year"))))

[Smygis]

its a simple formula.

(BasePopulation + (MoveinRate - MoveoutRate) * year) * year^(BirthRate - DeathRate)

If i remember my math correctly. Something i'm not sure of.

[Kvod10]

try using this to start

def popfunct(year):
    baseyear = 2004
    basepop = 26000
    birthrate = 0.007
    deathrate = 0.006
    movein = 300
    moveout = 325
 
    newpop = #...math...
 
    return newpop

when you make your GUI use float(int(raw_input("whatever you wanna say"))) for the input. I wouldn't just use int; your dealing with a lot of decimals

[Kvod10]

here's the function a little clearer

float(int(raw_input(" Prompt ")))

[bvdet]

@Kvod10
Thanks for posting Kvod10.

Actually, there is no need to convert to float in this case. An integer multiplied or divided by a float will return a float.

I would recommend type casting the appropriate data type. The input is supposed to be a year, therefore the appropriate data type is integer. A population count should be integer also. Since the rates are float, the interim calculation will produce a float which is necessary. The future population should therefore be cast to integer.

[imran akhtar]

below i have made the code, but comes up with error
message: TypeError: unsupported operand type(s) for ^: 'int' and 'float'

(result=(Basepop + (Movein - Moveout) * year) * year^(Birthrate - Deathrate) 
year=input("enter year:")
 
Birthrate = 0.007
Deathrate = 0.006
Movein = 300
Moveout = 325
Baseyear = 2004
Basepop=26000
 
 
result=(Basepop + (Movein - Moveout) * year) * year^(Birthrate - Deathrate)
 
print "estimated population", (result)

[bvdet]

Character "^" is the Python bitwise XOR operator symmetric difference operator for sets. I think you need the power operator "**".

[imran akhtar]

how would i power the operrator , is possiable if you could show
thanks

[bvdet]

The power operator works like this:

>>> 2**2
4
>>> 2**0.5
1.4142135623730951
>>> 

[imran akhtar]

sorry, i am confused with power operater, and i have now messed up my code lol, before it worked, after i made changes, it does work, and displays an arror messge such as

(result=(Basepop + (Movein - Moveout) * year) * year^(Birthrate - Deathrate)
TypeError: unsupported operand type(s) for ^: 'int' and 'float'

i have attched the code in txt file, so you can see problem.

[bvdet]

Replace "^" with "**":

year**(Birthrate - Deathrate)

-BV

[imran akhtar]

thanks it works, very greatful