Often, it is necessary to convert numbers from Nastran notation to float. For example, convert -5.75-3 into -5.75e-3.
We can write a simple python function for such conversion.

#Convert -5.75-3 into -5.75e-3 ?
def nastran2float(s):
    s = s.replace('-','e-')
    s = s.replace('+','e+')
    if s[0] == 'e':
        s = s[1:]
    return float(s)

x="-5.75-3"
z=nastran2float(x)
print(z)