Greg Greg - 11 days ago 6
Python Question

Display a decimal in scientific notation

How can I display this:

Decimal('40800000000.00000000000000') as '4.08E+10'?

I've tried this:

>>> '%E' % Decimal('40800000000.00000000000000')
'4.080000E+10'


But it has those extra 0's.

Answer
from decimal import Decimal

'%.2E' % Decimal('40800000000.00000000000000')

# returns '4.08E+10'

In your '40800000000.00000000000000' there are many more significant zeros that have the same meaning as any other digit. That's why you have to tell explicitly where you want to stop.

If you want to remove all trailing zeros automatically, you can try:

def format_e(n):
    a = '%E' % n
    return a.split('E')[0].rstrip('0').rstrip('.') + 'E' + a.split('E')[1]

format_e(Decimal('40800000000.00000000000000'))
# '4.08E+10'

format_e(Decimal('40000000000.00000000000000'))
# '4E+10'

format_e(Decimal('40812300000.00000000000000'))
# '4.08123E+10'
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