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I'm looking at prices of low-capitalization crypto meme coins. I want to format and show as a decimal in the print statement, up about 10 digits. For example, the price of Saitama as shown on CoinGekco is $0.000000100861.

I don't understand if I'm using the Decimal library wrong, or if this is just a print/formatting issue.

from decimal import Decimal
# I think everything after the 7663 is irrelevant, this is a number I'm getting back 
# from a Uniswap API.  It could be the price in ETH, that is my next issue.
price_float = 2.08229530000000007663121204885725199461299350645049344166181981563568115234375E-11
price_decimal = Decimal(str(price_float))
print("float:", price_float) 
print("decimal:", price_decimal)

Results:

float: 2.0822953e-11
decimal: 2.0822953E-11

Desired Results:

float: 2.0822953e-11
decimal: .000000000020822953

But if I try an exponent less than 6 it seems to work:

price_float = 2.08229530000000007663121204885725199461299350645049344166181981563568115234375E-6

Result:

decimal: 0.0000020822953000000003

Update 1 - based on comment/suggestion: Trying the formatting string. So a change to my question, do I need to bother with decimal at all, as long as I'm not adding numbers or maybe doing math on them?

print("float: {:10.14f}".format(price_float))
print("decimal: {:10.14f}".format(price_decimal))

Result:

float: 0.00000208229530
decimal: 0.00000208229530
NealWalters
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    Does this answer your question? [How to format a floating number to fixed width in Python](https://stackoverflow.com/questions/8885663/how-to-format-a-floating-number-to-fixed-width-in-python) – base12 Nov 12 '21 at 00:17
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    "Decimal" means "base 10". It doesn't mean "not scientific notation". `decimal.Decimal` internally uses a base 10 representation, but that doesn't mean it won't print in scientific notation. – user2357112 Nov 12 '21 at 00:17
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    Writing `price_float = 2.08229530000000007663` - never mind all the digits after that - is *utterly and completely useless*. Floats simply do not store numbers with that many significant digits of precision; turning this float into a Decimal later does not magically restore the lost precision. The only way to get the exact number into Decimal form is to pass it directly as a string. – jasonharper Nov 12 '21 at 00:26

2 Answers2

2

I do that

print(f'{price_float:.20f}')
print(f'{price_float:.20E}')

Output

0.00000000002082295300
2.08229530000000007663E-11
yoonghm
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1

You are probably looking for something like print("{:12.10f}".format(price_decimal)). The output format is not controlled here by the decimal library

base12
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