Round to 5 (or other number) in Python

Decoding the incantation

Adaptability and precision

Rounding may appear simple, but it's often a game of inches (or millimeters, for you metric folks 😉). You need to ensure you've got the accuracy where you need it at all times:

• Financial calculations: rounding to the nearest cent (that's 0.01, not 50 cents)
• Sensor data: rounded off to the nearest whole unit because decimals are just show-offs
• Mathematical simulations: a plethora of decimal places to keep things precise

Precision preserving practices

When dealing with rounded-off pennies or micro-units, cumulative discrepancies are your arch-nemesis. Enter the precision parameter in our trusty myround function:

• Ensures your accuracy game is on-point post-rounding
• Averts consecutive calculation drifts like a pro

Base flexibility: Bend it like Beckham

Whether you've got a thing for 2s (binary's favourite number), are feeling fractional, or just can't let go of 5s, our custom_round function flexes with you:

• base=2 for all those 1s and 0s-loving enthusiasts
• base=0.1 when you can't get enough of decimals

One-liner wizardry

Why raise an entire function when a single charm will do? Here’s a way to put Python's int and % operators to the test:

rounded_value = int(value) - int(value) % base  # Simple yet so clever


Beware of the bogarts

Floating-point phantoms

Floating-point arithmetic is often a trap for the unseasoned wizard—leading you astray with unexpected rounding errors. With great power comes great responsibility to understand binary representation. The Decimal module can be your Marauder's Map out of these haunted corridors.

Type turmoil

Always best to check what's in your cauldron before brewing a potion, lest it explodes! Wrong input types can lead to some unexpected and messy results. Be sure to:

• Validate the input like a responsible adult.
• Provide clear error messages for unsupported types, because nobody likes a cryptic menace.

Imagine a runners' track: each lane represents a number :

Track lanes: 🏃‍♂️ 0 | 1 | 2 | 3 | 4 | 🎯 5 | 6 | 7 | 8 | 9 | 🎯 10

The runner 🏃‍♂️ takes a break somewhere between two multiples of five:

So, to which 🎯 is our runner 🏃‍♂️ closer?

| Number | Rounded to 🎯 5 |
| ------ | --------------- |
| 3      | 🎯 5            |
| 7      | 🎯 5            |
| 11     | 🎯 10           |

Our run just turned into a game of "nearest 🎯 wins!".

Magical use cases

It's not all spells and charms

Sometimes, your base isn't an integer. But fear not, our custom function has got your back:

• Scale up your number by dividing with your base.
• Round off to the nearest whole number.
• Scale down by multiply back with the base.

Whew, disaster averted!

Optimizing the magic

Why compute when you can avoid it? If the input is already a multiple of the base, rounding is a no-op:

• This saves precious milliseconds in your computation.
• Easily checked with number % base == 0.

References