Python rounding does not work because of scientific number
Question:
Very simple, I want to round my ‘base_price’ and ‘entry’ with the precision, here 0.00001. It doesn’t work because it converts it to a scientific number.
How do I do this; I have been stuck for 1 hour.
Some post says to use output="{:.9f}".format(num) but it adds some zero after the last 1.
It work with precision = str(0.0001) but start from 4 zeros after the dot, it change to scientific numbers and digit = precision[::-1].find('.') doesn’t work with scientific numbers.
precision = str(0.00001) #5 decimals after the dot
print(precision)
base_price=0.0314858333
entry=0.031525
digit = precision[::-1].find('.')
entry_price = float(round(float(entry), digit))
base_price = float(round(float(base_price), digit))
print(entry_price,base_price)
Expected result:
base_price=0.03148 #5 decimals after the dot
entry=0.03152 #5 decimals after the dot
Answers:
If you want to round to a precision given by a variable, you can just do
precision = 0.00001
entry = 0.031525
entry_price = round(entry / precision) * precision
It sounds like you want to truncate the number, so:
precision = 0.00001
base_price = 0.0314858333
# use int to truncate the division to the nearest fraction.
base_price = int(base_price / precision) * precision
print(base_price) # prints 0.03148
To use numbers in the format ‘0.00001’ to set precision instead of the number you want, I’d use int(abs(math.log10(precision))) then pass that number to format.
Like so
import math
precision = 0.00001
precision_count = int(abs(math.log10(precision)))
base = 0.0314858333
entry = 0.031525
print(f"{entry:.{precision_count}f}, {base:.{precision_count}f}")
(I’ve removed suffix _price from base_price because in one case you used entry and entry_price and in the other you used base_price twice, so I went with the first standard for both)
I’d recommend you test with multiple possible values of precision
But, you probably should be using Decimal instead
Based on the variable names having "price", you could run into rounding problems/error compounding. To avoid surprises, I recommend you use decimal (or something with similar capabilities). In your case, quantize seems to be what you’re looking for.
Very simple, I want to round my ‘base_price’ and ‘entry’ with the precision, here 0.00001. It doesn’t work because it converts it to a scientific number.
How do I do this; I have been stuck for 1 hour.
Some post says to use output="{:.9f}".format(num) but it adds some zero after the last 1.
It work with precision = str(0.0001) but start from 4 zeros after the dot, it change to scientific numbers and digit = precision[::-1].find('.') doesn’t work with scientific numbers.
precision = str(0.00001) #5 decimals after the dot
print(precision)
base_price=0.0314858333
entry=0.031525
digit = precision[::-1].find('.')
entry_price = float(round(float(entry), digit))
base_price = float(round(float(base_price), digit))
print(entry_price,base_price)
Expected result:
base_price=0.03148 #5 decimals after the dot
entry=0.03152 #5 decimals after the dot
If you want to round to a precision given by a variable, you can just do
precision = 0.00001
entry = 0.031525
entry_price = round(entry / precision) * precision
It sounds like you want to truncate the number, so:
precision = 0.00001
base_price = 0.0314858333
# use int to truncate the division to the nearest fraction.
base_price = int(base_price / precision) * precision
print(base_price) # prints 0.03148
To use numbers in the format ‘0.00001’ to set precision instead of the number you want, I’d use int(abs(math.log10(precision))) then pass that number to format.
Like so
import math
precision = 0.00001
precision_count = int(abs(math.log10(precision)))
base = 0.0314858333
entry = 0.031525
print(f"{entry:.{precision_count}f}, {base:.{precision_count}f}")
(I’ve removed suffix _price from base_price because in one case you used entry and entry_price and in the other you used base_price twice, so I went with the first standard for both)
I’d recommend you test with multiple possible values of precision
But, you probably should be using Decimal instead
Based on the variable names having "price", you could run into rounding problems/error compounding. To avoid surprises, I recommend you use decimal (or something with similar capabilities). In your case, quantize seems to be what you’re looking for.