how to make output an input in python

Question

>>> import math

#defining first function
>>> def f(a):
        return a-math.sin(a)-math.pi/2

#defining second fuction
>>> def df(a):
        return 1-math.cos(a)

#defining third function which uses above functions
>>> def alpha(a):
        return a-f(a)/df(a)

How to write a code in which alpha(a) takes a starting value of a=2, and the solution of alpha(2) will become the input the next time. For eg: let's suppose alpha(2) comes to 2.39 , hence the next value would be alpha(2.39) and go on {upto 50 iterations}. Can somebody please help me a bit. thanks in advance.

Are you looking to do this while the program is running, or are you looking to be able to quit the application and continue with the last used number? — idjaw
– idjaw, Commented Jul 24, 2017 at 23:41

user94559 · Accepted Answer · 2017-07-24 23:43:47Z

2

You can let the program iterate with a for loop, and use a variable to store the intermediate results:

temp = 2                # set temp to the initial value
for _ in range(50):     # a for loop that will iterate 50 times
    temp = alpha(temp)  # call alpha with the result in temp
                        # and store the result back in temp
    print(temp)         # print the result (optional)

print(temp) will print the intermediate results. It is not required. It only demonstrates how the temp variable is updated throughout the process.

edited Jul 24, 2017 at 23:43

user94559

60.3k6 gold badges108 silver badges107 bronze badges

answered Jul 24, 2017 at 23:41

willeM_ Van Onsem

482k33 gold badges483 silver badges624 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Garry Saini Over a year ago

So, at some point the values keep repeating .Is there any program to choose the repeating value out of the 50 iteration??

willeM_ Van Onsem Over a year ago

@GarrySaini: usually if they start repeating, you can pick the last value. That means that you have found a fixed point of the program.

mypetlion · Accepted Answer · 2017-07-25 01:07:10Z

0

You can objectify it.

import math

class inout:
    def __init__(self, start):
        self.value = start
    def f(self, a):
        return a-math.sin(a)-math.pi/2
    def df(self, a):
        return 1-math.cos(a)
    def alpha(self):
        self.value = self.value-self.f(self.value)/self.df(self.value)
        return self.value

Then create an inout object and each time you call its alpha method it will give the next value in the series.

demo = inout(2)
print(demo.alpha())

answered Jul 25, 2017 at 1:07

mypetlion

2,5445 gold badges21 silver badges22 bronze badges

Collectives™ on Stack Overflow

how to make output an input in python

2 Answers 2

2 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related