How to check if a number is a power of another number using recursion in python

How do I make the is_power_of function return whether the number is a power of the given base? base is assumed to be a positive number.

def is_power_of[number, base]:
  # Base case: when number is smaller than base.
  if number < base:
    # If number is equal to 1, it's a power [base**0].
    return __

  # Recursive case: keep dividing number by base.
  return is_power_of[__, ___]

print[is_power_of[8,2]] # Should be True
print[is_power_of[64,4]] # Should be True
print[is_power_of[70,10]] # Should be False

SuperStormer

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asked May 14, 2020 at 12:16

1

def is_power_of[number, base]:
  # Base case: when number is smaller than base.
  if number < base:
    # If number is equal to 1, it's a power [base**0].
    return number == 1
  result = number//base
  # Recursive case: keep dividing number by base.
  return is_power_of[result, base]

answered Jul 27, 2020 at 6:46

ShishirShishir

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1

No recursion or brute force is required. Just logarithms.

When you have number = base ** x, you get x = log[number] / log[base]. Simply checking if x is an integer should give you the answer.

def is_power_of[number, base]:
    return [math.log[number] / math.log[base]].is_integer[]

If you want to handle negative numbers as well, you could just calculate x and then check that base ** x is equal to number

def is_power_of[number, base]:
    x = math.log[abs[number]] / math.log[abs[base]]
    return base ** x == number

answered Jul 15, 2020 at 15:59

Pranav HosangadiPranav Hosangadi

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2

The right way to do it is using recursion since it is asked in the chapter of this exercise.

So it will work like this

def is_power_of[number, base]:
# Base case: when number is smaller than base.
number= number/base
 if number < base:
# If number is equal to 1, it's a power [base**0].
  return False
 else: 
  return True
return is_power_of[number, base]


print[is_power_of[8,2]] # Should be True
print[is_power_of[64,4]] # Should be True
print[is_power_of[70,10]] # Should be False

answered Aug 17, 2020 at 1:25

1

def is_power_of[number, base]:
  # Base case: when number is smaller than base.
  if number < base:
    # If number is equal to 1, it's a power [base**0].
    if number == 1:
      return True

    else:
      return False
  # Recursive case: keep dividing number by base.
  return is_power_of[number/base , base]

print[is_power_of[8,2]] # Should be True
print[is_power_of[64,4]] # Should be True
print[is_power_of[70,10]] # Should be False

answered Jul 12, 2021 at 2:05

2

def is_power_of[number,base]:
    if number == base:
        return True
    elif number < base:
        return False
    return is_power_of[number / base, base]

It is done by recursion

answered Jul 15, 2020 at 14:27

3

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