CODEWITHSUNDEEP
pythonfloating-pointscientific-notation
Florian Oswald
Florian Oswald

Reputation: 5134

convert negative scientific notation 1.3E-2 to float?

I understand that I can convert a number in scientific notation to a float with float like this:

>>> x = 1.3e8
>>> float(x)
130000000.0

Then, why can I not do the same thing with a negative exponent?

>>> x = 1.3e-8
>>> x
1.3e-08
>>> float(x)
1.3e-08

I would have expected for float(x) in the last case to give 0.000000013

Upvotes: 1

Views: 3886

Answers (3)

abdullah.cu
abdullah.cu

Reputation: 684

The following function deals with an arbitrary number of floating points.

def displayfloat(x):
    # format numbers > 1.
    if str(x).find('+') > -1:
        return '{:.1f}'.format(x)
    e_idx = str(x).find('e')
    # format numbers > 1e-05
    if e_idx == -1:
        return str(x)
    # format numbers < 1e-05
    minus_idx = str(x).find('-')
    shift = e_idx
    if str(x).find('.') > -1:
        shift -= 1
    decimalpoints = -int(str(x)[str(x).find('-'):]) - 1 + shift
    floatformat = '{:.'+str(decimalpoints)+'f}'
    return floatformat.format(x)
# exmaples
displayfloat(1e-5) # --> '0.00001'
displayfloat(1.1e-5) # --> '0.000011'
displayfloat(1e+5) # --> '100000.0'

Upvotes: 0

Eugene Yarmash
Eugene Yarmash

Reputation: 149806

1.3e-8 is a floating point literal (i.e. it directly creates a float object) so you don't need to wrap it in a float(). The Python shell simply returns the default string representation of a float. To force the fixed-point notation, you can use str.format(), although you may need to specify the precision:

>>> '{:.9f}'.format(1.3e-8)
'0.000000013'

Upvotes: 1

Tobey
Tobey

Reputation: 1440

It is already a float, it just stays represented in scientific notation

print(type(1.3e8)) # <class 'float'>
print(type(1.3e-8)) # <class 'float'>
print(0.000000013)  # 1.3e-08

Upvotes: 0

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