How to convert a E notation string to a float with fixed exponent in python

Question

My instrumentation device returns strings of data such as 2.89E-6, 9.87E-1, 4.18E-4 etc.

How can I change the representation such that the exponent is always -3. My intention is to manually extract the Mantissa of the resultant expression.

Desired output:

string 2.89E-6 becomes-> float 0.00289E-3

string 9.87E-1 becomes-> float 987E-3

string 4.18E-4 becomes-> float 0.418E-3

Eventually, would like to extract the mantissa-> 0.000289, 987, 0.418 respectively as my “final” output.

Answer 1

You can use the decimal module for manipulation of decimal numbers, then convert to float at the end if needed.

import decimal

data = ['2.89E-6', '9.87E-1', '4.18E-4']

for s in data:
    n = decimal.Decimal(s)
    print(float(n * 1000))

Output:

0.00289
987.0
0.418