While loop does not show any output

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Please find time to answer this question.

When I print the following code, my while loop does not show any output.

Python

import math
epsilon=.000000001

def mysqrt(a):
    while True:
       x=a/2
       y=(x+a/x)/2
       if abs(y-x)<epsilon:
 return (y)

def test_square_root():
 a=1.0
 print ('a'," ","mysqrt(a)"," ","math.sqrt(a)"," ","diff")
 while a<10.0:
   print(a," ",mysqrt(a)," ",math.sqrt(a)," ",abs(mysqrt(a)-math.sqrt(a)))
   a+=1
 
test_square_root()

What I have tried:

I am trying to solve Allen Downey's 7.1.

For the time being i am not concerned about the format of the table. I need the following output. What is missing in my code?

a mysqrt(a) math.sqrt(a) diff
- --------- ------------ ----
1.0 1.0 1.0 0.0
2.0 1.41421356237 1.41421356237 2.22044604925e-16
3.0 1.73205080757 1.73205080757 0.0
4.0 2.0 2.0 0.0
5.0 2.2360679775 2.2360679775 0.0
6.0 2.44948974278 2.44948974278 0.0
7.0 2.64575131106 2.64575131106 0.0
8.0 2.82842712475 2.82842712475 4.4408920985e-16
9.0 3.0 3.0 0.0

Posted 9-Oct-23 23:57pm

Baziga

Updated 10-Oct-23 23:30pm

Richard Deeming

v2

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OriginalGriff · Answer 1 · 2023-10-10T00:15:00

Indentation in Python is significant: it controls what is and isn't in a block of code.
All the contiguous code indented by the same amount (or more) is part of the same code block:

Python

while foo == bar:
    Part of loop
    if (foo + bar == foobar:
        Still part of loop
Not part of loop - executed once the loop exits.

So your lack of indentation on the return statement means it isn't a part of the if or the while.
As a result, there is no way out of the loop and your app never does anything.

Indent it properly, and it should start to work:

Python

def mysqrt(a):
    while True:
       x=a/2
       y=(x+a/x)/2
       if abs(y-x)<epsilon:
           return(y)

However, you should note that you don't alter a or epsilon inside the loop, so either it will exit after the first iteration, or never ...