how to change for loop to while loop

Question

I'm trying to have this while loop give the same output as the for-loop, however, its infinitely recursive as opposed to stopping at the maximum average height.

The code looks like this:

import numpy as np
N = 5
h = np.zeros(N) # heights of family members (in meter)
h[0] = 1.60; h[1] = 1.85; h[2] = 1.75; h[3] = 1.80; h[4] = 0.50
sum = 0
i = 0
while i < 5:
     sum = sum + h[i]
     average = sum/n
     print('average height: {:g} meter'.format(average))

This is the for loop I was trying to get the while loop of:

for i in [0, 1, 2, 3, 4]:
    sum = sum + h[i]
    average = sum/N
    print(’Average height: {:g} meter’.format(average))

Where did I go wrong?

expected output:

average height 0.64 meter
average height 1.01 meter
average height 1.36 meter
average height 1.72 meter
average height 1.82 meter

Where do you change i?

Mr. T
– Mr. T

2020-12-01 11:23:38 +00:00
Commented Dec 1, 2020 at 11:23 — Mr. T
– Mr. T, Commented Dec 1, 2020 at 11:23

Martin Kleiven · Accepted Answer · 2020-12-03 23:48:37Z

4

It looks like you are trying to calculate the running average, printing the current value as you go. For this you don't need numpy... or do you?

Simply define a list containing your heights. Then iterate through it.

heights = [1.6, 1.85, 1.75, 1.80, 0.5]

running_sum = 0.0
running_average = 0.0
for height in heights:
    running_sum += height
    running_average = running_sum / len(heights)

    print('Current average height: {:g} meter'.format(running_average))

It looks like the final value for the average height in the family is 1.5, not really 1.82, as your expected output says. Which can be verified with WolframAlpha. We have another problem too it seems. Your running average so far divides by the total length (5) every time, when we should divide by the length thus far. That's something you might want to use numpy for. For that, see this question on running averages.

Old answer below:

Remember to increment the counter i:

Remember that sum is already defined in Python. So I changed it's name to s, and collapsed the operation s = s + h[i] to s += h[i]

i = 0
while i < 5:
    s += h[i]
    average = sum/n
    print('average height: {:g} meter'.format(average))
    i+=1

edited Dec 3, 2020 at 23:48

answered Dec 1, 2020 at 11:23

Martin Kleiven

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4 Comments

ppwater Over a year ago

It' doesn't get the expected output

Mr. T Over a year ago

NameError: name 'n' is not defined

Mr. T Over a year ago

Now with added NameError: name 's' is not defined

ppwater Over a year ago

Why this is highly upvoted when it has many problems?

ppwater · Accepted Answer · 2020-12-01 11:45:09Z

0

Martin Kleiven's answer does solve the repeating problem, but it gives an error. here is the correct answer:

Remember to increment the counter i:

import numpy as np
N = 5
h = np.zeros(N) # heights of family members (in meter)
h[0] = 1.60; h[1] = 1.85; h[2] = 1.75; h[3] = 1.80; h[4] = 0.50
s = 0
i = 0
while i < 5:
     s = s + h[i] # by the way, sum is already defined in python, so change the variable name.
     average = s/N # Change it to n => N
     print('average height: {:g} meter'.format(average))
     i += 1

answered Dec 1, 2020 at 11:45

ppwater

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