How to select a range of values in a pandas dataframe column?

.between is a good solution, but if you want finer control use this:

(0.5 <= df['two']) & (df['two'] < 0.5)

The operator & is different from and. The other operators are | for or, ~ for not. See this discussion for more info.

Your statement was the same as this:

(0.5 <= df['two']) and (df['two'] < 0.5)

Hence it raised the error.

Use between with inclusive=False for strict inequalities:

df['two'].between(-0.5, 0.5, inclusive=False)

The inclusive parameter determines if the endpoints are included or not (True: <=, False: <). This applies to both signs. If you want mixed inequalities, you'll need to code them explicitly:

(df['two'] >= -0.5) & (df['two'] < 0.5)