extract number from exponent in Python

Question

Hi everyone / Python Gurus

I would like to know how to accomplish the following task, which so far I've been unable to do so.

Here's what I have:

Q1 = 20e-6

Now this is an exponential number that if you print(Q1) as is it will show: 2e-5 which is fine. Mathematically speaking.

However, here's what I want to do with it:

I want Q1 to print only the number 20. And based on the whether this is e-6 then print uC or if this e-9 the print nC.

Here's an example for better understanding:

Q1=20e-6

When I run print(Q1) show: 20uC.

Q2=20e-9

When I run print(Q2) show: 20nC.

Can you please help me figure this out?

Answer 1

I recommend you using si-prefix.

You can install it using pip:

sudo pip install si-prefix

Then you can use something like this:

from si_prefix import si_format

# precision after the point
# char is the unity's char to be used
def get_format(a, char='C', precision=2):
    temp = si_format(a, precision)

    try:
        num, prefix = temp.split()
    except ValueError:
        num, prefix = temp , ''

    if '.' in num:
        aa, bb = num.split('.')
        if int(bb) == 0:
            num = aa

    if prefix:
        return num + ' ' + prefix + char
    else:
        return num


tests = [20e-6, 21.46e05, 33.32e-10, 0.5e03, 0.33e-2, 112.044e-6]
for k in tests:
    print get_format(k)

Output:

20 uC
2.15 MC
3.33 nC
500
3.30 mC
112.04 uC