Develop Reference

Python bisection search confusion

I'm trying to work on the MIT intro to CS with Python problem set 1.
Here's the problem (bottom of page 3):
https://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-0001-introduction-to-computer-science-and-programming-in-python-fall-2016/assignments/MIT6_0001F16_ps1.pdf
Here's my code:
#best savings rate in 3 years
annual_salary = float(input("Enter your annual salary: "))
total_cost = 1000000
semi_annual_raise = 0.07
portion_down_payment = 0.25*total_cost
r = 0.04
low = 0
high = 10000
pre_saved = int((high+low)/2)
steps = 0
current_savings = 0
epsilon = 100
months = 0
salary_increase_months = 0
portion_saved = pre_saved/10000
print(portion_saved)
while abs(current_savings - portion_down_payment) >= epsilon:
#calculates savings after 36 months
while(months < 36):
#checks every 6th iteration to add the semi annual raise
if(salary_increase_months == 6):
annual_salary += annual_salary*semi_annual_raise
salary_increase_months = 0
current_savings += current_savings*(r/12) + portion_saved*(annual_salary/12)
salary_increase_months += 1
months += 1
#print(current_savings)
#bisection search portion
if current_savings < portion_down_payment - epsilon:
#print('1')
low = portion_saved*10000
current_savings = 0
elif current_savings > portion_down_payment + epsilon:
#print('2')
high = portion_saved*10000
current_savings = 0
elif current_savings < portion_down_payment + epsilon and current_savings > portion_down_payment - epsilon:
print('Best savings rate:', portion_saved)
print('Steps in bisection search:', steps)
break
else:
print('It is not possible to pay the down payment in three years.')
break
portion_saved = int((low + high)/2)
portion_saved = portion_saved/10000
steps += 1
months = 0
salary_increase_months = 0
When I put in a value for the salary, all I get is the original percentage saved (0.5) and the output doesn't end. Nothing else gets printed. I created three if statements that are supposed to check the value of portion saved and do a bisection search (if the value is higher than portion down payment plus epsilon, then high becomes the portion saved, and vice versa).

def curr_saving(salary, Semi_raise, saveP, month):
saving = 0
monthly_income = salary/12
# down_pay = 0.25*cost
for i in range(1, month):
if i % 6 == 0:
salary += salary*Semi_raise
monthly_income = salary/12
interest = saving*(1+0.04/12)
saving = monthly_income*saveP+interest
return saving
def Hunting_C(base, Semi_raise, cost):
# saving = 0
# salary = base
# monthly_income = salary/12
down_pay = 0.25*cost
No_month = 36
# saving_range = numpy.arange(0, 1, 0.0001)
step = 0
min_S = 0
max_S = 1
saveP = (min_S+max_S)/2
while (abs(curr_saving(base, Semi_raise, saveP, No_month)-down_pay)) >= 100:
step += 1
if curr_saving(base, Semi_raise, saveP, No_month) > down_pay:
max_S = saveP
else:
min_S = saveP
saveP = (min_S+max_S)/2
return f'saving rate: {saveP}, No of steps: {step}, current saving: {curr_saving(base, Semi_raise, saveP, No_month)}'
print(Hunting_C(150000, 0.07, 1000000))

questions repeated 4x, float not callable, error on code

I dont understand why the code doesnt work and they have repeated the questions to me 4 times. and say that float is not callable. i have tried doing this for quite awhile but i dont seem to get anything at all. is there any easier way for python3? I just learnt this language 2 weeks ago. its not a whole new world to me but many of the things i am not familiar with. such as indentation
def get_taxi_info():
flag_down = float(input("What's the flag-down fare: $"))
within = float(input("What's the rate per 400 meters within 9.8km? $"))
beyond = float(input("What's the rate per 350 meters beyond 9.8km? $"))
distance = float(input("What's the distance traveled (in meters)? "))
peak = input("Is the ride during a peak period? [yes/no]")
mid6 = input("Is the ride between midnight and 6am? [yes/no]")
location = input("Is there any location surcharge? [yes/no]")
surloca = float(input("What's the amount of location surcharge?"))
return (flag_down, within, beyond, distance, peak == 'yes', mid6 == 'yes', location == 'yes', surloca)
def calculate_taxi_fare():
dist = get_taxi_info()
if dist[3] > 9800:
extra = (dist[3] - 9800) % 350
if extra == 0:
a = (extra//350) + 22
else:
a = (extra//350) + 23
return a
elif dist[3] <= 9800:
extra = (dist[3] - 1000) % 400
if extra == 0:
a = (extra//400)
else:
a = (extra//400) + 1
return a
def peakornot():
peak = get_taxi_info()
if peak[4] == True and peak[5] == False:
surcharge = 1.25
return surcharge
elif peak[4] == False and peak[5] == True:
surcharge = 1.50
return surcharge
taxifare = calculate_taxi_fare()
info = get_taxi_info()
peak1 = peakornot()
taxifare = calculate_taxi_fare()
if info[6] == True:
payable = ((info[0] + (info[1] * taxifare()) + (info[2] * taxifare())) * peak1[0]) + info[7]
print ("The total fare is $" + str(payable))
elif info[6] == False:
payable = ((info[0] + (info[1] * taxifare()) + (info[2] * taxifare())) * peak1[0]) + info[7]
print ("The total fare is $" + str(payable))

The function calculate_taxi_fare returns a float, so on this line taxifare is a float
taxifare = calculate_taxi_fare()
Therefore you cannot say taxifare() because it looks like a function call, so you can just use for example
info[1] * taxifare

Function not defined, although its been defined... Going Insane

So I am quite new to python and have been working on this assignment for a week now on and off and can't quite get it to run correctly. I am now getting errors that tell me the function get_in_code is not defined although I've defined it. Any help would be greatly appreciated!
SENTINEL = 'XXX'
DAY_CHARGE = 1500.00
#Define get_days
def get_days():
good_data = False
while not good_data:
try:
n_days = int(input("Please enter the number of days you stayed: "))
except ValueError:
print("Error, Bad Data")
else:
if n_days > 0:
good_data = True
else:
print("This is bad data, please re enter data")
return n_days
#define get_cost(p)
def get_cost():
cost = float(input("Please enter the cost for the procedures: "))
while cost < 0:
print("Procedure cost cant be negative: ")
cost = float(input("Please enter the cost for the procedures: "))
return cost
#define med cost
def med_cost():
med_cost = float(input("Enter the cost of your medicine: "))
while med_cost < 0:
print("Medicine cost cant be negative: ")
med_cost = float(input("Enter the cost of your medicine: "))
return med_cost
#Find day cost
def find_day_cost(in_code, n_days):
day_cost = n_days * DAY_CHARGE
if in_code == 'ZH':
p_day_cost = day_cost * 0.20
in_day_cost = day_cost *0.80
elif in_code == 'HH':
p_day_cost = day_cost * 0.10
in_day_cost = day_cost * 0.90
elif in_code == 'CH':
p_day_cost = day_cost * 0.25
in_day_cost = day_cost * 0.75
else:
p_day_cost = day_cost
in_day_cost = 0
return p_day_cost, in_day_cost
#find procedure cost
def find_proc_cost(in_code, cost):
if in_code == 'ZH':
p_proc_cost = 0
in_proc_cost = cost
elif in_code == 'HH':
p_proc_cost = cost * 0.10
in_proc_cost = cost * 0.90
elif in_code == 'CH':
p_proc_cost = cost * 0.50
in_proc_cost = cost * 0.50
else:
p_proc_cost = cost
in_proc_cost = 0
return p_proc_cost, in_proc_cost
#find medicine cost
def find_med_cost(in_code, med_cost):
if in_code == 'ZH':
p_med_cost = 0
in_med_cost = med_cost
elif in_code == 'HH':
p_med_cost = med_cost * 0.10
in_med_cost = med_cost * 0.90
elif in_code == 'CH':
p_med_cost = med_cost * 0.50
in_med_cost = med_cost * 0.50
else:
p_med_cost = med_cost
in_med_cost = 0
return p_med_cost, in_med_cost
#Display pat_info
def display_pat_info(pat_name, in_name):
print("City Hospital - Patient Invoice")
print("Patient Name: ", pat_name)
print("Insurance: ", in_name)
#display day cost
def display_day_cost(p_day_cost, in_day_cost):
print("Patient Day Cost: ", p_day_cost,"\tInsurance Day Cost: ", in_day_cost)
#display procedure cost
def display_proc_cost(p_proc_cost, in_proc_cost):
print("Patient Procedure Cost: ", p_proc_cost, "\tInsurance Procedure Cost: ", in_proc_cost)
#display medicine cost
def display_med_cost(p_med_cost, in_med_cost):
print("Patient Medicine Cost: ", p_med_cost, "\tInsurce Medicine Cost: ", in_med_cost)
#Display totals
def display_totals(total_pat, total_in):
print("Total Billed To Patient: ", total_pat, "\tTotal Billed To Insurance: ", total_in, "\tTotal Bill: ", (total_pat + total_in))
#display day_totals
def display_day_totals(total_zip, total_happy, total_cheap, total_pat):
print("City Hospital - End Of Day Billing Report")
print("Total Dollar Amount Billed Today: ", total_zip+total_happy+total_cheap+total_pat)
print("Total Billed To Zippy Healthcare: ", total_zip)
print("Total Billed To Happy Healthcare: ", total_happy)
print("Total Billed To Cheap Healthcare: ", total_cheap)
print("Total Billed To Uninsured: ", total_pat)
#display day_counts()
def display_day_counts(zip_count, happy_count, cheap_count, no_in_count):
print("The total amount of Zippy Healthcare patients is: ", zip_count)
print("The total amount of Happy Healthcare patients is: ", happy_count)
print("The total amount of Cheap Healthcare patients is: ", cheap_count)
print("The total amount of Uninsured patients is: ", no_in_count)
#def main
def main():
#Counters and accumulators
total_zip= 0.00
total_cheap= 0.00
total_happy= 0.00
total_pat= 0.00
zip_count= 0
cheap_count= 0
happy_count= 0
no_in_count= 0
total_in = 0
#Open file
try:
Pat_File = open('PatientBill.txt', 'w')
except ValueError:
print("*****ERROR***** - Corrupt File")
else:
file_exist = True
#Priming read
pat_name = input("Please enter the patients name: (XXX to stop program)")
#Processing loop
while pat_name != SENTINEL:
#Input data
in_code = get_in_code()
num_days = get_days()
proc_cost = get_cost()
med_cost = med_cost()
#find each cost
pat_day, insure_day = find_day_cost(in_code, num_days)
pat_proc, insure_proc = find_proc_cost(in_code, proc_cost)
pat_med, insure_med = find_med_cost(in_code, med_cost)
#update accumulators and totals
total_pat += pat_day + pat_proc + pat_med
if in_code == 'ZH':
zip_count += 1
total_zip += in_day_cost + in_proc_cost + in_med_cost
in_name = 'Zippy Healthcare'
elif in_code == 'HH':
happy_count += 1
total_happy += in_day_cost + in_proc_cost + in_med_cost
in_name = 'Happy Healthcare'
elif in_code == 'CH':
cheap_count += 1
total_cheap += in_day_cost + in_proc_cost + in_med_cost
in_name = 'Cheap Healthcare'
else:
no_in_count += 1
in_name = 'Uninsured'
total_in = total_zip + total_happy + total_cheap
#displays patients invoice
display_pat_info(pat_name,in_name)
display_day_cost(pat_day, insure_day)
display_proc_cost(pat_proc, insure_proc)
display_med_cost(pat_med, insure_med)
display_totals(pat_day + pat_proc + pat_med, insure_day + insure_proc + insure_med)
#Write output to file
if file_exist:
Pat_File.write(pat_name, pat_day+pat_med+pat_proc )
#Get next patients name
pat_name = input("Please enter the patients name: (XXX to stop program)")
#Close the output file
if file_exist:
Pat_File.close()
#display the accumlators and totals
display_day_totals(total_zip, total_happy, total_cheap, total_pat)
display_day_counts(zip_count,happy_count,cheap_count,no_in_count)
#define get_in_code
def get_in_code():
in_code = input("Please enter one of the insurance codes, ZH, CH, HH, XX")
while in_code not in ('ZH', 'HH', 'CH', 'XX'):
print("***Please enter a proper insurance code***")
in_code = input("Please enter one of the insurance codes, ZH, CH, HH, XX")
return in_code
main()

Python is a interpreted language. You need to define function prior to its usage. Just move a function definitions at the top of a file.
The problem is also with indentation. You're defining your methods inside while, just after a return statement. Actual functions aren't defined at all - interpreter doesn't reach those lines.
Besides, the code is "dirty". Split the code into separate classes/modules. Create well defined areas of responsibility, that would improve the code and it'll be easier to work with it.

Python raw input function for tax calculation

I am trying to make a simple calculator for working out the tax due on a salary. Please see the code below:
I keep getting this error and I don't know what is wrong, please help :) thanks!
Traceback (most recent call last):
File "python", line 13
elif salary > 11000 and salary < 43000:
^
SyntaxError: invalid syntax
CODE:
salary = raw_input ("What is your salary?")
print "So your gross annual salary is %r GBP" % (salary)
print "\nNow we need to calculate what your net salary is."
def taxes(salary):
salary >= 0
while true:
if salary < 11000:
tax = 0
elif salary > 11000 and salary < 43000:
tax = (0.2 * income) - 2200
elif salary > 43000 and salary < 150000:
tax = (0.4 * (salary - 43000)) + 6400
elif salary > 150000:
tax = ((salary - 150000) * 0.45) + 6400 + 42800
return tax

Steps to correct your code
step1 : the salary data type should be of int, to correct..use the following code
step 2: Indentation is compulsory in python, so indent your code very well
step 3: Add an else statement after the conditional statements
step 4: indent return statement
change your code to this one
salary = int(raw_input ("What is your salary?"))
print "So your gross annual salary is %r GBP" % (salary)
print "\nNow we need to calculate what your net salary is."
def taxes(salary):
salary >= 0
while true:
if salary < 11000:
tax = 0
elif salary > 11000 and salary < 43000:
tax = (0.2 * income) - 2200
elif salary > 43000 and salary < 150000:
tax = (0.4 * (salary - 43000)) + 6400
elif salary > 150000:
tax = ((salary - 150000) * 0.45) + 6400 + 42800
else :
tax = undefined
return tax

It felt like there was a better way of doing this, so I came up with an alternative route:
tax_bands = [11000, 43000, 150000]
tax_amts = [0.2, 0.4, 0.45]
salary = 43001
Placing the thresholds and amounts into a list means that you can change them more easily if you need to.
The function below creates a list of the tax calculations, tax_list, and then a separate list of the maximum tax liability in each band called max_tax (the upper band has no maximum).
It then compares the values in the lists, and overwrites the tax_list if the corresponding value is larger than the maximum.
Then it calculates the sum of all values in tax_list greater than zero and returns it.
def taxes(salary, tax_bands, tax_amts):
tax_list = [(pct * (salary - band)) for (band, pct) in zip(tax_bands, tax_amts)]
max_tax = []
for index, sal in enumerate(tax_bands[:-1]):
max_tax.append(tax_bands[index + 1] - sal)
max_tax = [segment * tax for segment, tax in zip(max_tax, tax_amts[:-1])]
for index, value in enumerate(tax_list):
try:
if value > max_tax[index]:
tax_list[index] = max_tax[index]
except:
pass
tax_to_pay = sum([x for x in tax_list if x > 0])
return tax_to_pay
print taxes(salary, tax_bands, tax_amts)
salary = input ("What is your salary?")
print "So your gross annual salary is %r GBP" % (salary)
print "\nYour net annual salary is: {} GBP".format(salary - taxes(salary, tax_bands, tax_amts))
To be super safe, you could also have the first line in the function call int(salary) using a try except just to check that it's the right type and that someone hasn't entered 43,000.

That because there are indent error in line number 12, now you can just copy pust this :
note : salary > 11000 and salary < 43000 equivalent to 11000 < salary < 43000 in python:
salary = raw_input ("What is your salary?")
print "So your gross annual salary is %r GBP" % (salary)
print "\nNow we need to calculate what your net salary is."
def taxes(salary):
while true:
if salary < 11000:
tax = 0
elif 11000 < salary < 43000:
tax = (0.2 * income) - 2200
elif salary > 43000 and salary < 150000:
tax = (0.4 * (salary - 43000)) + 6400
elif salary > 150000:
tax = ((salary - 150000) * 0.45) + 6400 + 42800
return tax

As the comments have already stated, your indentation is incorrect. See below:
def taxes(salary):
salary >= 0
tax = 0
if salary < 11000:
tax = 0
elif salary > 11000 and salary < 43000:
tax = (0.2 * income) - 2200
elif salary > 43000 and salary < 150000:
tax = (0.4 * (salary - 43000)) + 6400
elif salary > 150000:
tax = ((salary - 150000) * 0.45) + 6400 + 42800
print("Value of tax is: " + str(tax))
return tax
salary = raw_input ("What is your salary?")
print "So your gross annual salary is %r GBP" % (salary)
print "\nNow we need to calculate what your net salary is."
print("\nHere is your net salary after taxes: %r" % (taxes(int(salary))))
With python, indentations are how you tell the interpreter which blocks of code fall where (unlike with Java for example with semicolons being the end of line delimiter). By not indenting properly on your elif statements, you are essentially telling the program there is an elif without an if hence your syntax problem.

Calculating a total cost in Python

I'm trying to create a trip planner in python, but after I defined all the functions I'm not able to call and calculate them in the last function tripCost().
In tripCost, I want to put the days and travel destination (city) and the program runs the functions and gives me the exact result of all the 3 functions previously defined.
Code:
def hotelCost():
days = raw_input ("How many nights will you stay at the hotel?")
total = 140 * int(days) print "The total cost is",total,"dollars"
def planeRideCost():
city = raw_input ("Wich city will you travel to\n")
if city == 'Charlotte':
return "The cost is 183$"
elif city == 'Tampa':
return "The cost is 220$"
elif city == 'Pittsburgh':
return "The cost is 222$"
elif city == 'Los Angeles':
return "The cost is 475$"
else:
return "That's not a valid destination"
def rentalCarCost():
rental_days = raw_input ("How many days will you rent the car\n")
discount_3 = 40 * int(rental_days) * 0.2
discount_7 = 40 * int(rental_days) * 0.5
total_rent3 = 40 * int(rental_days) - discount_3
total_rent7 = 40 * int(rental_days) - discount_7
cost_day = 40 * int(rental_days)
if int(rental_days) >= 3:
print "The total cost is", total_rent3, "dollars"
elif int(rental_days) >= 7:
print "The total cost is", total_rent7, "dollars"
else:
print "The total cost is", cost_day, "dollars"
def tripCost():
travel_city = raw_input ("What's our destination\n")
days_travel = raw_input ("\nHow many days will you stay\n")
total_trip_cost = hotelCost(int(day_travel)) + planeRideCost (str(travel_city)) + rentalCost (int(days_travel))
return "The total cost with the trip is", total_trip_cost
tripCost()

Your def rentalCarCost(): is returning nothing..
rentalCost (int(days_travel)) I can't see such function.
Update:
def hotelCost():
days = raw_input ("How many nights will you stay at the hotel?")
total = 140 * int(days) print "The total cost is",total,"dollars"
return total
def planeRideCost():
city = raw_input ("Wich city will you travel to\n")
if city == 'Charlotte':
return 183
elif city == 'Tampa':
return 220
elif city == 'Pittsburgh':
return 222
elif city == 'Los Angeles':
return 475
else:
print "That's not a valid destination"
def rentalCarCost():
rental_days = raw_input ("How many days will you rent the car\n")
discount_3 = 40 * int(rental_days) * 0.2
discount_7 = 40 * int(rental_days) * 0.5
total_rent3 = 40 * int(rental_days) - discount_3
total_rent7 = 40 * int(rental_days) - discount_7
cost_day = 40 * int(rental_days)
if int(rental_days) >= 3:
print "The total cost is", total_rent3, "dollars"
return total_rent3
elif int(rental_days) >= 7:
print "The total cost is", total_rent7, "dollars"
return total_rent7
else:
print "The total cost is", cost_day, "dollars"
return cost_day
def tripCost():
travel_city = raw_input ("What's our destination\n")
days_travel = raw_input ("\nHow many days will you stay\n")
total_trip_cost = hotelCost(int(day_travel)) + planeRideCost () + rentalCarCost(int(days_travel))
return "The total cost with the trip is", total_trip_cost
tripCost()

I suggest you separate user interaction from calculations. I made some changes, and I am pasting it as an example, I am not saying this code does the right thing for your problem, it is just to illustrate that separation. You can also use a cost_table as a dictionary:
cost_table = {
'Charlotte':183,
'Tampa':220,
'Pittsburgh':222,
'Los Angeles':475
}
def hotel_cost(nights):
cost = 140 * int(nights)
return cost
def plane_ride_cost(city):
return cost_table[city]
def rental_car_cost(days):
discount_3 = 40 * days * 0.2
discount_7 = 40 * days * 0.5
total_rent3 = 40 * days - discount_3
total_rent7 = 40 * days - discount_7
cost_day = 40 * days
if days >= 3:
return total_rent3
elif days >= 7:
return total_rent7
else:
return cost_day
def trip_cost(city, nights, car_days):
total = hotel_cost(nights) + plane_ride_cost(city) +\
rental_car_cost(car_days)
return total
city = None
while True:
city = raw_input ("What's our destination?\n")
if city not in cost_table:
print "That's not a valid destination."
else:
break
hotel_nights = raw_input ("\nHow many nights will you stay?\n")
car_days = raw_input ("How many days will you rent the car?\n")
total_trip_cost = hotel_cost(int(hotel_nights)) +\
plane_ride_cost(city) +\
rental_car_cost(int(car_days))
print "The total cost with the trip is", total_trip_cost, "dollars."