How to shorten a decimal in python
You want to round your answer. Show
Here's some examples of this unpredictable behavior:
Assuming your intent is to do the traditional rounding for statistics in the sciences, this is a handy wrapper to
get the
Aha! So based on this we can make a function...
Basically this adds a really small value to the string to force it to round up properly on the unpredictable instances where it doesn't ordinarily with the The approach of using So the finished code will be something like:
...should give you the results you expect. You can also use the decimal library to accomplish this, but the wrapper I propose is simpler and may be preferred in some cases. Edit:
Thanks Blckknght for pointing out that the When we truncate values, we remove the decimal portion of a value. But what if we want to keep a certain number of decimal places? Let’s see how to program that in Python. IN THIS ARTICLE:
# Truncate values in Python to a certain number of decimalsWith Python’s So what to do instead? Luckily, with just a bit of code we can make our own function that truncates to decimal places. Here’s how that code looks:
This custom To validate we use
Python’s cascaded if statement. Its first condition checks with Then we see if the The last condition checks if Now we get to the second part of the function. This is where we truncate to a certain number of decimal places. First we determine the correction factor. For that
we raise Then we call the Say we want to truncate To use the custom
Truncation is something else than rounding. When we truncate, we throw away any fractional value. But the value before the decimal point ( # Examples: truncate to a number of decimal digitsNow that we got a custom function that truncates to a certain number of decimal places, let’s see how we use it. # Truncate single Python values to a decimal amountOne option is to call
Here we first import the Then we make three variables, Next we truncate those variables to three decimal places. For that we call The final statements output the results with Python’s
# Truncate a sequence to decimal places with a list comprehensionWe may also need to truncate every value in a list or array. If that truncation is all we have to do, then a list comprehension is an easy and efficient approach. This example program does just that:
This mini-program first imports the Then a list comprehension truncates each value in that list to 2
decimal places. For that we loop through the list with an in-line The last bit of code uses
If you don’t have to keep the original values, then you can also set the list to the outcome of the list comprehension:
# Truncate a list to decimal places with a for loopNot every situation can use a list comprehension. If we want to do other
tasks on each list value, and then truncate it, a Here’s a quick example that truncates list values with Python’s
Here we again first import the Next we make a list of random floating-point values ( We make that loop next. This The example ends with two
By the way, if
your program doesn’t need to keep the original list, you can also overwrite that list with its truncated values. An easy way to do that is with Python’s
FURTHER READING
Published December 20, 2019. « All Python math articles How do you shorten a decimal?Put simply, if the last digit is less than 5, round the previous digit down. However, if it's 5 or more than you should round the previous digit up. So, if the number you are about to round is followed by 5, 6, 7, 8, 9 round the number up. And if it is followed by 0, 1, 2, 3, 4 round the number down.
How do you truncate to 2 decimal places in Python?Just use the formatting with %. 2f which gives you round down to 2 decimal points.
What is .2f in Python?2f is a placeholder for floating point number. So %d is replaced by the first value of the tuple i.e 12 and %. 2f is replaced by second value i.e 150.87612 .
How do you truncate to 4 decimal places in Python?With Python's math. trunc() function we truncate floating-point values into whole numbers (Python Docs, n.d.). That turns 4.578 into 4 and makes -2.9 into -2 . But that function always truncates to an integer, without an option to keep a certain number of decimal places.
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