Enforce that numeric output has at least two trailing decimal places, including trailing zeros

Question

I have a Python script that produces the following output:

Please note the numbers 31.7, 31.8, 31.9.

The purpose of my script is to determine numeric palindromes, such as 1.01.

The problem with the script (reproduced below) is that it will evaluate numeric palindromes such as 1.1 as valid- however- that is not considered to be valid output in this situation.

Valid output needs to have exactly two decimal places.

How to enforce that the numeric output has at least two trailing decimal places, including trailing zeros?

import sys

# This method determines whether or not the number is a Palindrome
def isPalindrome(x):
    x = str(x).replace('.','')
    a, z = 0, len(x) - 1
    while a < z:
        if x[a] != x[z]:
            return False
        a += 1
        z -= 1
    return True

if '__main__' == __name__:

    trial = float(sys.argv[1])

    operand = float(sys.argv[2])

    candidrome = trial + (trial * 0.15)

    print(candidrome)
    candidrome = round(candidrome, 2)

    # check whether we have a Palindrome
    while not isPalindrome(candidrome):
        candidrome = candidrome + (0.01 * operand)
        candidrome = round(candidrome, 2)
        print(candidrome)

    if isPalindrome(candidrome):
        print( "It's a Palindrome! " + str(candidrome) )

Possible duplicate of print float to n decimal places including trailing 0's — Zach Gates
– Zach Gates, Commented Sep 23, 2017 at 3:17

Zach Gates · Accepted Answer · 2017-09-23 03:03:55Z

1

You can use the builtin format function. .2 refers to the number of digits, and f refers to "float".

if isPalindrome(candidrome):
    print("It's a Palindrome! " + format(candidrome, '.2f'))

Or:

if isPalindrome(candidrome):
    print("It's a Palindrome! %.2f" % candidrome)

edited Sep 23, 2017 at 3:03

answered Sep 23, 2017 at 2:54

Zach Gates

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3 Comments

smatthewenglish Over a year ago

does this turn it into a string?

Zach Gates Over a year ago

@s.matthew.english: Yes it does. Something like format(0.666666, '.2f') will return '0.67'.

smatthewenglish Over a year ago

but I need it to be as a float so I can pipe it back into the function and make it a palindrome

John Zwinck · Accepted Answer · 2017-09-23 02:52:39Z

1

Try this instead of str(x):

twodec = '{:.2f}'.format(x)

answered Sep 23, 2017 at 2:52

John Zwinck

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1 Comment

smatthewenglish Over a year ago

I still see the pernicious non-trailing-zeroers, like this 3.2

Ajax1234 · Accepted Answer · 2017-09-23 02:53:04Z

0

You can try this:

data = """
    1.7
    31.71
    31.72
    31.73
  """
new_data = data.split('\n')
palindromes = [i for i in new_data if len(i) > 3 and i.replace('.', '') == i.replace('.', '')[::-1]]

answered Sep 23, 2017 at 2:53

Ajax1234

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FluffyKitten · Accepted Answer · 2017-09-23 10:31:17Z

0

x = ("%.2f" % x).replace('.','')

edited Sep 23, 2017 at 10:31

FluffyKitten

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answered Sep 23, 2017 at 2:53

leyanpan

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1 Comment

FluffyKitten Over a year ago

Code-only answers are discouraged because they do not explain how they resolve the issue in the question. Consider updating your answer to explain what this does and how it addresses the problem - this will help not just the OP but others with similar issues. Please review How do I write a good answer

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