How can I use boolean inddex arrays to filter a list without using numpy?

For example:

```
>>> l = ['a','b','c']
>>> b = [True,False,False]
>>> l[b]

```

The result should be:

```
['a']

```

I know numpy support it but want to know how to solve in Python.

```
>>> import numpy as np
>>> l = np.array(['a','b','c'])
>>> b = np.array([True,False,False])
>>> l[b]
array(['a'], 
      dtype='|S1')

```