You want to print the numbers in decimal format with 16 digits precision? How about this?
a = [-2.75090260e-08, 3.11586226e-08, 1.86128266e-08, -1.01560789e-07]
print map(lambda x: "{0:.16f}".format(x), a)
This prints
['-0.0000000275090260', '0.0000000311586226', '0.0000000186128266', '-0.0000001015607890']
Update:
You don't even need the lambda. Using
map("{0:.16f}".format, a)
works just as well. Thanks @JaminSore for pointing that out.