Converting a list of integers into a single integer

nooniensoong97
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Hi,

So here's what I have to convert an interger into a list of integers. pie = pi.n(digits = 10) pies = list(pie.str()) pies.remove('.') pies = [int(i) for i in pies]

output: [3,1,4,1,5,9,2,6,5,3]

So after manipulating this list of integers I would like to then reverse the process to create a new integer. The only way I can think of is to take each item, and multiply them by the factor. ie. zero term wouldn't need to be multiplied, but the first term in list would be multiplied by 0.1, second would be multiplied by 0.01, and then add them all up. Is there an easier way of converting back to an integer?

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What do you mean when you say "integer"?

John Palmieri ( 3 years ago )

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answered 3 years ago

John Palmieri

8906 ●20 ●74 ●193 http://www.math.washin...

updated 3 years ago

Sage integers have a digits method which returns the list of digits, with units digit last, preceded by 10's digit, etc.:

sage: a = 31415
sage: a.digits()
[5, 1, 4, 1, 3]

So you could do:

sage: pie = pi.n(digits = 10)
sage: pied = (pie * 10**10).trunc() # get an integer
sage: pied
31415926535
sage: pi_digits = pied.digits()
sage: pi_digits
[5, 3, 5, 6, 2, 9, 5, 1, 4, 1, 3]
sage: sum(10**index * digit for (index, digit) in enumerate(pi_digits))
31415926535

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Thanks. However, sage truncates the value down to 14 digits after trying to multiple to get the sum back down to 3.141.... I am working on something other then pi, and I would like to try and keep the nth digits in the numbers I am working with.

nooniensoong97 ( 3 years ago )

What is n in your case? How many digits are you trying to keep?

John Palmieri ( 3 years ago )

n will increase by one each iteration. I am not sure how far I will run the program right now I am just in the debug phase.

nooniensoong97 ( 3 years ago )

What have you tried, what part of my suggestion isn't working? Can you just replace "10" in my suggestion with "m" and then increase m each time? If you want more help, you need to provide more details about what you're trying to accomplish.

John Palmieri ( 3 years ago )

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Converting a list of integers into a single integer

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