[python] How can I format a decimal to always show 2 decimal places?

I want to display:

49 as 49.00

and:

54.9 as 54.90

Regardless of the length of the decimal or whether there are are any decimal places, I would like to display a Decimal with 2 decimal places, and I'd like to do it in an efficient way. The purpose is to display money values.

eg, 4898489.00

This is the same solution as you have probably seen already, but by doing it this way it's more clearer:

>>> num = 3.141592654

>>> print(f"Number: {num:.2f}")

You should use the new format specifications to define how your value should be represented:

>>> from math import pi  # pi ~ 3.141592653589793
>>> '{0:.2f}'.format(pi)
'3.14'

The documentation can be a bit obtuse at times, so I recommend the following, easier readable references:

• the Python String Format Cookbook: shows examples of the new-style .format() string formatting
• pyformat.info: compares the old-style % string formatting with the new-style .format() string formatting

Python 3.6 introduced literal string interpolation (also known as f-strings) so now you can write the above even more succinct as:

>>> f'{pi:.2f}'
'3.14'

If you're using this for currency, and also want the value to be seperated by ,'s you can use

$ {:,.f2}.format(currency_value).

e.g.:

currency_value = 1234.50

$ {:,.f2}.format(currency_value) --> $ 1,234.50

Here is a bit of code I wrote some time ago:

print("> At the end of year " + year_string + " total paid is \t$ {:,.2f}".format(total_paid))

> At the end of year   1  total paid is         $ 43,806.36
> At the end of year   2  total paid is         $ 87,612.72
> At the end of year   3  total paid is         $ 131,419.08
> At the end of year   4  total paid is         $ 175,225.44
> At the end of year   5  total paid is         $ 219,031.80   <-- Note .80 and not .8
> At the end of year   6  total paid is         $ 262,838.16
> At the end of year   7  total paid is         $ 306,644.52
> At the end of year   8  total paid is         $ 350,450.88
> At the end of year   9  total paid is         $ 394,257.24
> At the end of year  10  total paid is         $ 438,063.60   <-- Note .60 and not .6
> At the end of year  11  total paid is         $ 481,869.96
> At the end of year  12  total paid is         $ 525,676.32
> At the end of year  13  total paid is         $ 569,482.68
> At the end of year  14  total paid is         $ 613,289.04
> At the end of year  15  total paid is         $ 657,095.40   <-- Note .40 and not .4  
> At the end of year  16  total paid is         $ 700,901.76
> At the end of year  17  total paid is         $ 744,708.12
> At the end of year  18  total paid is         $ 788,514.48
> At the end of year  19  total paid is         $ 832,320.84
> At the end of year  20  total paid is         $ 876,127.20   <-- Note .20 and not .2

The String Formatting Operations section of the Python documentation contains the answer you're looking for. In short:

"%0.2f" % (num,)

Some examples:

>>> "%0.2f" % 10
'10.00'
>>> "%0.2f" % 1000
'1000.00'
>>> "%0.2f" % 10.1
'10.10'
>>> "%0.2f" % 10.120
'10.12'
>>> "%0.2f" % 10.126
'10.13'

.format is a more readable way to handle variable formatting:

'{:.{prec}f}'.format(26.034, prec=2)

The OP always wants two decimal places displayed, so explicitly calling a formatting function, as all the other answers have done, is not good enough.

As others have already pointed out, Decimal works well for currency. But Decimal shows all the decimal places. So, override its display formatter:

class D(decimal.Decimal):
    def __str__(self):
        return f'{self:.2f}'  

Usage:

>>> cash = D(300000.991)
>>> print(cash)
300000.99

Simple.

The Easiest way example to show you how to do that is :

Code :

>>> points = 19.5 >>> total = 22 >>>'Correct answers: {:.2%}'.format(points/total) `

Output : Correct answers: 88.64%

You can use the string formatting operator as so:

num = 49
x = "%.2f" % num  # x is now the string "49.00"

I'm not sure what you mean by "efficient" -- this is almost certainly not the bottleneck of your application. If your program is running slowly, profile it first to find the hot spots, and then optimize those.

if you have multiple parameters you can use

 print('some string {0:.2f} & {1:.2f}'.format(1.1234,2.345))
 >>> some string 1.12 & 2.35

>>> print "{:.2f}".format(1.123456)
1.12

You can change 2 in 2f to any number of decimal points you want to show.

EDIT:

From Python3.6, this translates to:

>>> print(f"{1.1234:.2f}")
1.12

In python 3, a way of doing this would be

'{:.2f}'.format(number)

what about

print round(20.2564567 , 2)    >>>>>>>        20.25


print round(20.2564567 , 4)    >>>>>>>        20.2564