# 5 Best Ways to Convert Base 3 to Integer in Python

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π‘ Problem Formulation: Converting numbers from base 3 (ternary) to integers (base 10) is a frequent requirement in various coding scenarios. For instance, you might be working with a numerical system that operates in base 3 and need to interpret its values in a more conventional base 10 format. An example of the input could be a ternary string ‘12012’ and the desired output would be an integer 142.

## Method 1: Using the int() Function with Base Specified

Python’s built-in `int()` function can convert a string representation of a number in a specified base directly to an integer. The function takes two arguments: the string to be converted and the base of the number system. Specifying base 3 for the second argument will convert a ternary string to an integer.

Here’s an example:

```ternary_number = '12012'
integer_number = int(ternary_number, 3)
print(integer_number)```

Output:

142

In this example, we convert the ternary string ‘12012’ to its integer representation by passing it alongside the base ‘3’ to the `int()` function. The function returns the integer value 142, which is the base 10 equivalent of the ternary number.

## Method 2: Manual Conversion Using Loop

Another way to convert a ternary number to an integer is by manually parsing the string and applying mathematical operations. The process involves iterating over each digit, multiplying it by 3 raised to the power of its position index (from right to left, starting at 0), and summing up the results to get the base 10 integer.

Here’s an example:

```ternary_number = '12012'
integer_number = 0
for index, digit in enumerate(reversed(ternary_number)):
integer_number += int(digit) * (3 ** index)
print(integer_number)```

Output:

142

This snippet manually calculates the base 10 equivalent of the ternary number by reversing the number string, iterating over each digit, and adding its contribution to the final integer value. This is a good alternative when you need to avoid built-in functions or wish to have a deeper understanding of the conversion process.

## Method 3: Using List Comprehension and sum()

List comprehension in Python offers a concise way to perform operations on a listβs elements. In conjunction with the `sum()` function, it can be used to perform the base conversion by creating a list of each digit’s contribution to the base 10 value and summing the elements in the list.

Here’s an example:

```ternary_number = '12012'
integer_number = sum(int(digit) * (3 ** index) for index, digit in enumerate(reversed(ternary_number)))
print(integer_number)```

Output:

142

This method takes a functional approach, using a generator expression inside the `sum()` function to compute the equivalent integer. This technique is more pythonic and can be faster for shorter strings than manual loops, though for very long strings, memory usage could be a concern.

## Method 4: Using functools.reduce()

The `functools.reduce()` function can also be used for converting a base 3 number to integer. This function reduces a list to a single cumulative value by applying a binary function cumulatively to the items of a list, from left to right. Here, we combine it with `lambda` for the mathematical operations involved in the conversion.

Here’s an example:

```from functools import reduce
ternary_number = '12012'
integer_number = reduce(lambda x, y: x*3 + int(y), ternary_number, 0)
print(integer_number)```

Output:

142

In this snippet, the `reduce()` function with a `lambda` expression acts as an accumulator, starting with 0 and applying the mathematical operation for each digit in the string. It’s a compact, functional programming way to solve the problem.

## Bonus One-Liner Method 5: Using the map() Function

If you’re a fan of one-liners, Python’s `map()` function can be a handy tool when used with `sum()` and list comprehension. It applies a function to all the items in an input list. Here, we use it to convert the individual digits before summing.

Here’s an example:

```ternary_number = '12012'
integer_number = sum(map(lambda x: int(x[1]) * (3 ** x[0]), enumerate(reversed(ternary_number))))
print(integer_number)```

Output:

142

This method combines `map()` with `lambda`, `enumerate()`, and `sum()` to perform the base conversion in a single line. It’s elegant but may be harder to understand for those unfamiliar with Python’s functional programming aspects.

## Summary/Discussion

• Method 1: Using int() Function with Base Specified. Strengths: Simple, clean, and uses built-in Python functionality. Weaknesses: Not suitable if the base conversion mechanism needs to be customized beyond what is provided by the function.
• Method 2: Manual Conversion Using Loop. Strengths: Easy to understand the conversion process step by step; no need for Python’s built-in functions. Weaknesses: More verbose and might be slower for large strings compared to built-in methods.
• Method 3: Using List Comprehension and sum(). Strengths: More pythonic and possibly faster for short strings. Weaknesses: Potentially high memory usage with very long strings due to list comprehension.
• Method 4: Using functools.reduce(). Strengths: Functional programming approach, compact code. Weaknesses: Might be less intuitive for those unfamiliar with reduce or lambda expressions.
• Method 5: Using the map() Function. Strengths: Concise one-liner, functional programming style. Weaknesses: Can be cryptic and hard to read, especially for Python novices.