# 4 Methods to Count Decimal Places in Python Float Numbers

## How to Count Decimal Places in Python Float Numbers

Python is a powerful programming language with a vast library of built-in functions and modules that make it easy to perform complex mathematical operations. One of the most common tasks in programming is counting decimal places in a float number.

In this article, we will explore various ways to accomplish this task using Python.

### Method 1: Using String Manipulation

The first method involves using string manipulation to count decimal places in a float.

To do this, we first convert the float to a string using the `str()` function. Then we find the position of the decimal point using the `str.find()` method and subtract it from the length of the string.

Here’s the code:

``````num = 3.14159
decimal_places = len(str(num)) - str(num).find('.') - 1

print(decimal_places)
``````

In this example, we have a float number `3.14159`. We convert it to a string using `str(num)`, which gives us `'3.14159'`.

Then we use `str.find('.')` method to find the position of the decimal point, which is 1. Finally, we subtract 1 from the length of the string (`'3.14159'`) to get the number of decimal places, which is 5.

### Method 2: Using Decimal Class

The second method involves using the `Decimal` class from the `decimal` module to count decimal places in a float. The `Decimal` class provides a built-in method called `as_tuple()` that returns a tuple representing the number in scientific notation.

We can use the exponent value in the tuple to calculate the number of decimal places. Here’s the code:

``````from decimal import Decimal

num = Decimal('3.14159')
exponent = num.as_tuple().exponent
decimal_places = abs(exponent)

print(decimal_places)
``````

In this example, we create a `Decimal` object using the string `'3.14159'`. Then we use the `as_tuple()` method to get the tuple representation of the number, which is `(1, (3, 1, 4, 1, 5), -5)`.

The exponent value is `-5`, which means the decimal point is 5 digits to the left of the rightmost digit. We take the absolute value of the exponent to get the number of decimal places, which is 5.

### Method 3: Using Split() Method

The third method involves using the `split()` method to count decimal places in a float. We first convert the float to a string using the `str()` function, then split it into two parts using the `split()` method.

The first part contains the digits before the decimal point, and the second part contains the digits after the decimal point. We can then count the number of digits in the second part to get the number of decimal places.

Here’s the code:

``````num = 3.14159
decimal_places = len(str(num).split('.')[-1])

print(decimal_places)
``````

In this example, we convert the float number `3.14159` to a string using the `str()` function. Then we split it into two parts using the `split()` method, which gives us `['3', '14159']`.

Finally, we get the length of the second part (`'14159'`) to get the number of decimal places, which is 5.

### Method 4: Using re.sub() Method

The fourth method involves using the `re.sub()` method from the `re` module to count decimal places in a float.

We use a regular expression to replace all the digits before the decimal point with an empty string, leaving only the digits after the decimal point. Then we count the number of digits in the resulting string to get the number of decimal places.

Here’s the code:

``````import re

num = 3.14159
decimal_places = len(re.sub(r'd+.', '', str(num)))

print(decimal_places)
``````

In this example, we convert the float number `3.14159` to a string using the `str()` function. Then we use the `re.sub()` method to replace all the digits before the decimal point with an empty string.

The regular expression `'d+.'` matches one or more digits followed by a decimal point. The resulting string is `'.14159'`.

We get the length of the resulting string to get the number of decimal places, which is 5.

## Conclusion

In this article, we have discussed four different methods to count decimal places in a float using Python. The first method involved using string manipulation, the second method involved using the `Decimal` class, the third method involved using the `split()` method, and the fourth method involved using the `re.sub()` method.

Each method has its own advantages and disadvantages and can be used depending on the requirements of the task at hand. By understanding these methods, you will be better equipped to handle similar tasks in your own programming projects.

Counting decimal places in Python float numbers is a common task in programming, and there are several methods to accomplish it, including string manipulation, using the `Decimal` class, using the `split()` method, and using the `re.sub()` method. Each method has its advantages and disadvantages and can be used depending on the task’s requirements.

By understanding these methods, programmers can tackle similar challenges with greater ease.