Question

I am trying write a program in python to calculate heart rate training zones (using Karvonen’s formula for anyone who is interested 🙂 ).

The formula is different for men and women but both require age (alder), resting heart rate (hvilepuls) and max heart rate (makspuls).

The code calculates max heart rate if the individual just presses enter.

I wanted to catch blank inputs for age and resting heart, and also values inputted for all three variables that are zero or less.

I have been able to catch blank inputs but I cannot seem to combine it with the zero or less ones as well.

The code I have written is below and works but does not stop people enter numbers that are equal to or less than zero.

Any other general comments about cleaning-up the code and better (more pythonic perhaps?) ways of writing this are much appreciated.

# Karvonens formel
#
print(
"""
Kalkulere dine treningssoner for lett løping, anaerob terskel (AT) og VO2 Max treningsøkter.

Instruksjoner

1. Fyll inn din alder, hvilepuls og kjønn.
2. Skriv inn din maksimale hjertefrekvens, hvis du vet det, ellers trykk enter - deretter beregnet programmet det selv som følger:
(Menn 214 - (0,8 * alder) Kvinner:. 209 - (0,7 * alder).

3. Treningssonenes verdier beregnes ved hjelp av Karvonen formelen:
X% = (Maksimal hjertefrekvens hvilepuls) * x/100) + hvilepuls
"""
)

kjonn=""
alder=""
hvilepuls=""
makpuls=""


while kjonn.lower() != "m" and kjonn.lower() != "d":
    kjonn = input("Hvilken kjønn er du? (M)ann/(D)ame\t")

while alder=="":
    alder = int(input("Hvor mange år er du?\t"))

while hvilepuls=="":
    hvilepuls = int(input("Hva er din hvilepuls?\t"))

makspuls = input("Hva er din makspuls?\t")


if makspuls=="":
    if kjonn.lower()=="m":
        makspuls = int(214 - 0.8*int(alder))
    elif kjonn.lower() =="d":
        makspuls = int(209 - 0.7*int(alder))
    else:
        print("\n\nEnter M or D")
else:
    makspuls=int(makspuls)

prosent60 = (makspuls-hvilepuls)*0.6 + hvilepuls
prosent75 = (makspuls-hvilepuls)*0.75 + hvilepuls
prosent85 = (makspuls-hvilepuls)*0.85 + hvilepuls
prosent90 = (makspuls-hvilepuls)*0.9 + hvilepuls

# Remove decimals
prosent60 = int(prosent60)
prosent75 = int(prosent75)
prosent85 = int(prosent85)
prosent90 = int(prosent90)


print("\n\n")
if kjonn.lower()=="m":
    print("Din kjønn  er:\t\tMann")
else:
    print("Din kjønn  er:\t\tDame")
print("Din alder er:\t\t", alder)
print("Din hvilepuls er:\t", hvilepuls," slag/min")
print("Din makspuls er:\t", makspuls," slag/min")

print("\n\n")
print("Din lavsone er:\t",prosent60,"-",prosent75," slag/min")
print("Din ATsone er:\t",prosent85,"-",prosent90," slag/min")
print("Din VO2max er:\t",prosent90,"-",makspuls," slag/min")


input("\n\nTrykk enter for å avslutte")

Answer 1

Here is what I suggest.

• Input should be validated, and cleaned up, immediately. Usually when you take input, it is a good idea to call the .strip() method, in case the user entered extra spaces or tabs by mistake. Right after you read the 'm' or 'd' value, force it to lower-case; then the rest of the code can assume it is lower-case.

• When you want to check one value against multiple possible legal values, a good Python idiom is to use in (value0, value1, value2, ..., valueN). In this case you could check in ('m', 'd'), but because we are checking for a single character, we can actually just check in "md" and that works too.

• When you want to allow an empty string or an integer, just read the response into a temp variable (I used the name s for “string temporary variable”) and then you can check for a zero-length string; if it is not zero-length, convert to an integer. You could initialize your integer variable to a negative value, and then loop until it is not negative; but I prefer to use the while True: loop and add an explicit break to show the success condition that breaks out. (Note: if this is homework, your teacher may not agree with me; some teachers don’t like to see break inside a loop, but rather prefer testing the loop only at the top.)

• I added some error messages. I put “@@@@@” around my text to help make sure you find it all and localize it to your language. (It’s a short program so likely you could have found them all anyway, but I wanted to make it as easy as possible for you.)

• Instead of calling int() on floating-point numbers to convert them to integer, I used round(), so that 77.9 will become 78 rather than 77.

EDIT: I just edited the code. I broke out the input validation into a function, with a “validator” function you pass in. I think it is cleaner this way.

Code:

# Karvonens formel
#
print(
"""
Kalkulere dine treningssoner for lett lping, anaerob terskel (AT) og VO2 Max treningskter.

Instruksjoner

1. Fyll inn din alder, hvilepuls og kjnn.
2. Skriv inn din maksimale hjertefrekvens, hvis du vet det, ellers trykk enter - deretter beregnet programmet det selv som flger:
(Menn 214 - (0,8 * alder) Kvinner:. 209 - (0,7 * alder).

3. Treningssonenes verdier beregnes ved hjelp av Karvonen formelen:
X% = (Maksimal hjertefrekvens hvilepuls) * x/100) + hvilepuls
"""
)

kjonn=' '
alder=0
hvilepuls=0
makpuls=' '

def check_positive(n):
    if n > 0:
        return True
    else:
        print("@@@@@ Cannot enter a negative or 0 value! @@@@@")
        return False
def check_positive_or_zero(n):
    if n >= 0:
        return True
    else:
        print("@@@@@ Cannot enter a negative value! @@@@@")
        return False

def get_input_int(s_mesg, fn_validate, default=None):
    while True:
        s = input(s_mesg).strip()
        if not s and default is not None:
            return default
        # not a default value; try it as an int
        try:
            n = int(s)
        except ValueError:
            print("@@@@@ Not even an integer! @@@@@")
            continue
        # works as an int; is it valid?
        if fn_validate(n):
            return n


while kjonn not in ('m', 'd'):
    kjonn = input("Hvilken kjnn er du? (M)ann/(D)ame\t").strip().lower()

alder = get_input_int("Hvor mange r er du?\t", check_positive)
hvilepuls = get_input_int("Hva er din hvilepuls?\t", check_positive)
makspuls = get_input_int("Hva er din makspuls?\t", check_positive_or_zero, default=0)


if not makspuls:
    if kjonn == 'm':
        makspuls = int(214 - 0.8*int(alder))
    else:
        makspuls = int(209 - 0.7*int(alder))

prosent60 = (makspuls-hvilepuls)*0.6 + hvilepuls
prosent75 = (makspuls-hvilepuls)*0.75 + hvilepuls
prosent85 = (makspuls-hvilepuls)*0.85 + hvilepuls
prosent90 = (makspuls-hvilepuls)*0.9 + hvilepuls

# Remove decimals
prosent60 = round(prosent60)
prosent75 = round(prosent75)
prosent85 = round(prosent85)
prosent90 = round(prosent90)


print("\n\n")
if kjonn == 'm':
    print("Din kjnn  er:\t\tMann")
else:
    print("Din kjnn  er:\t\tDame")

print("Din alder er:\t\t", alder)
print("Din hvilepuls er:\t", hvilepuls," slag/min")
print("Din makspuls er:\t", makspuls," slag/min")

print("\n\n")
print("Din lavsone er:\t",prosent60,"-",prosent75," slag/min")
print("Din ATsone er:\t",prosent85,"-",prosent90," slag/min")
print("Din VO2max er:\t",prosent90,"-",makspuls," slag/min")


input("\n\nTrykk enter for avslutte")