Rounding of a Value in Python

Question

Can Python disable or not used the rounding off a float?

This is my sample

value = 6.30 * 75.73

value:

477.099

I want only to get the value 477.09 without rounding it off.

Answer 1

You can try this hack with round:

>>> 6.30 * 75.73
>>> 477.099

>>> DIGITS = 2

>>> round(6.30 * 75.73 - 5.0 * 10**(-DIGITS-1), DIGITS)
>>> 477.09

Answer 2

Possibly this? (takes about 100 nanoseconds independent of number of digits)

** note, this does not work for negative numbers as written, so it's of limited use.

value = 6.30 * 75.73
print value
print value - value % 0.01

477.097
477.09

does it really truncate?

value = 1./3.
print value - 0.33333333  # see the leftovers
3.333333331578814e-09

print value - value % 0.01
0.33

print (value - value % 0.01) - 0.33  # no leftovers
0.0

(value - value % 0.01) == 0.33
True

Answer 3

convert value to string(if value an integer then the code will still work, because before the conversion to a string we convert to a float):

value = = 6.30 * 75.73
value_str = str(float(value))

'{:.2f}'.format(float(value_str[:value_str.index('.') + 3]))

Answer 4

What you want is called truncating, which is notoriously difficult with float values because of the way they are stored.

If you are doing this for the value itself, you can do this;

value = 6.30 * 75.73
value = (( value * 100 ) // 1) * .01

print(value)

This will print

477.09000000000003

which is equivalent to 477.09 for math calculations.

If you are doing this to display the value, then you can convert to a string and just cut off the last digit that you have. Or, if you don't know how many digits there are after the decimal point, you can get the index of the ".", and cut everything that is 2 after that point, as so:

value = 6.30 * 75.73
val_str = str(value)
rounded_str = val_str[:val_str.index('.') + 3]

This will print

477.09

Answer 5

You can convert to a string and using string split, append just the last 2 digits of the number

num = 477.097
strnum = str(int(num)) + str(num).split(".")[1][:2]