How to Display Decimals in Scientific Notation with Two Significant Figures in Python?

Displaying Decimals in Scientific Notation

Converting a decimal number to scientific notation involves formatting the number to display its significant figures in a concise and standardized way. This is often useful for displaying large or small numbers concisely.

Problem:

How can we display a decimal value like Decimal('40800000000.00000000000000') in scientific notation with two significant figures, resulting in a string like '4.08E 10'?

Solution:

The Decimal module in Python provides a convenient way to specify a decimal value. To display it in scientific notation, we can use the %E format specifier as follows:

>>> '%.2E' % Decimal('40800000000.00000000000000')
'4.08E+10'

This approach works well for formatting decimals. However, it may sometimes include additional trailing zeros in the exponent. To remove these zeros, we can split the string on the E character and manually remove them:

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'

This function effectively removes any trailing zeros in the exponent, ensuring a concise and readable scientific notation string.

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