How do you print float to 2 decimal places in python?

Question

TLDR ;)

The rounding problem of input and output has been solved definitively by Python 3.1 and the fix is backported also to Python 2.7.0.

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Documentation
How to display a float with two decimal places?
How do you get value to 2 decimal places in Python?
How do you print float up to 2 decimal places?
How do you use .2f in Python?

Rounded numbers can be reversibly converted between float and string back and forth:
str -> float() -> repr() -> float() ... or Decimal -> float -> str -> Decimal

>>> 0.3
0.3
>>> float(repr(0.3)) == 0.3
True

A Decimal type is not necessary for storage anymore.

Results of arithmetic operations must be rounded again because rounding errors could accumulate more inaccuracy than that is possible after parsing one number. That is not fixed by the improved repr() algorithm (Python >= 3.1, >= 2.7.0):

>>> 0.1 + 0.2
0.30000000000000004
>>> 0.1, 0.2, 0.3
(0.1, 0.2, 0.3)

The output string function str(float(...)) was rounded to 12 valid digits in Python < 2.7x and < 3.1, to prevent excessive invalid digits similar to unfixed repr() output. That was still insufficientl after subtraction of very similar numbers and it was too much rounded after other operations. Python 2.7 and 3.1 use the same length of str() although the repr() is fixed. Some old versions of Numpy had also excessive invalid digits, even with fixed Python. The current Numpy is fixed. Python versions >= 3.2 have the same results of str() and repr() function and also output of similar functions in Numpy.

Test

import random
from decimal import Decimal
for _ in range(1000000):
    x = random.random()
    assert x == float(repr(x)) == float(Decimal(repr(x)))  # Reversible repr()
    assert str(x) == repr(x)
    assert len(repr(round(x, 12))) <= 14         # no excessive decimal places.

Documentation

See the Release notes Python 2.7 - Other Language Changes the fourth paragraph:

Conversions between floating-point numbers and strings are now correctly rounded on most platforms. These conversions occur in many different places: str() on floats and complex numbers; the float and complex constructors; numeric formatting; serializing and de-serializing floats and complex numbers using the marshal, pickle and json modules; parsing of float and imaginary literals in Python code; and Decimal-to-float conversion.

Related to this, the repr() of a floating-point number x now returns a result based on the shortest decimal string that’s guaranteed to round back to x under correct rounding (with round-half-to-even rounding mode). Previously it gave a string based on rounding x to 17 decimal digits.

The related issue

More information: The formatting of float before Python 2.7 was similar to the current numpy.float64. Both types use the same 64 bit IEEE 754 double precision with 52 bit mantissa. A big difference is that np.float64.__repr__ is formatted frequently with an excessive decimal number so that no bit can be lost, but no valid IEEE 754 number exists between 13.949999999999999 and 13.950000000000001. The result is not nice and the conversion repr(float(number_as_string)) is not reversible with numpy. On the other hand: float.__repr__ is formatted so that every digit is important; the sequence is without gaps and the conversion is reversible. Simply: If you perhaps have a numpy.float64 number, convert it to normal float in order to be formatted for humans, not for numeric processors, otherwise nothing more is necessary with Python 2.7+.

Use str.format() with “{:.2f}” as string and float as a number to display 2 decimal places in Python. Call print and it will display the float with 2 decimal places in the console.

Simple example code use str.format(number) with “{:.2f}” as string and float as a number to return a string representation of the number with two decimal places.

fnum = 7.154327

res = "{:.2f}".format(fnum)

print(res)

Output:

How do you print float to 2 decimal places in python?

How to display a float with two decimal places?

Answer: Use the string formatting operator for that:

>>> '%.2f' % 1.234
'1.23'
>>> '%.2f' % 5.0
'5.00'

OR

print("{:.2f}".format(5))

Do comment if you have any doubts and suggestions on this Python decimal places code.

Note: IDE: PyCharm 2021.3.3 (Community Edition)
Windows 10
Python 3.10.1

All Python Examples are in Python 3, so Maybe its different from python 2 or upgraded versions.

Degree in Computer Science and Engineer: App Developer and has multiple Programming languages experience. Enthusiasm for technology & like learning technical.

How do you get value to 2 decimal places in Python?

As expected, the floating point number (1.9876) was rounded up to two decimal places – 1.99. So %. 2f means to round up to two decimal places.

How do you print float up to 2 decimal places?

we now see that the format specifier "%. 2f" tells the printf method to print a floating point value (the double, x, in this case) with 2 decimal places.

How do you use .2f in Python?

A format of . 2f (note the f ) means to display the number with two digits after the decimal point. So the number 1 would display as 1.00 and the number 1.5555 would display as 1.56 .

programming python Decimal Python Format float Python Float Python

How do you print float to 2 decimal places in python?

TLDR ;)

Test

Documentation

How to display a float with two decimal places?

How do you get value to 2 decimal places in Python?

How do you print float up to 2 decimal places?

How do you use .2f in Python?

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