Setting a fixed number of decimal places globally is often a bad idea since it is unlikely that it will be an appropriate number of decimal places for all of your various data that you will display regardless of magnitude. Instead, try this which will give you scientific notation only for large and very small values (and adds a thousands separator unless you omit the ","):
pd.set_option('display.float_format', lambda x: '%,g' % x)
Or to almost completely suppress scientific notation without losing precision, try this:
pd.set_option('display.float_format', str)