Dive Into Python 3

APPENDIX A ■ PORTING CODE TO PYTHON 3 WITH 2TO3

306

filter() Global Function

In Python 2, the filter() function returned a list, the result of filtering a sequence through a function

that returned True or False for each item in the sequence. In Python 3, the filter() function returns an

iterator, not a list, as shown in Table A-16.

Table A-16. filter() Returns an Iterator

Notes Python 2 Python 3

(1)

filter(a_function, a_sequence) list(filter(a_function, a_sequence))

(2)

list(filter(a_function, a_sequence))

No Change

(3)

filter(None, a_sequence) [i for i in a_sequence if i]

(4)

i

in filter(None, a_sequence):

No Change

(5)

[i for i in filter(a_function, ...