item_08.py

#!/usr/bin/env python3

# Copyright 2014 Brett Slatkin, Pearson Education Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

# Preamble to mimick book environment
import logging
from pprint import pprint
from sys import stdout as STDOUT


# Example 1
matrix = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
flat = [x for row in matrix for x in row]
print(flat)


# Example 2
squared = [[x**2 for x in row] for row in matrix]
print(squared)


# Example 3
my_lists = [
    [[1, 2, 3], [4, 5, 6]],
    [[7, 8, 9], [10, 11, 12]],
]
flat = [x for sublist1 in my_lists
        for sublist2 in sublist1
        for x in sublist2]
print(flat)


# Example 4
flat = []
for sublist1 in my_lists:
    for sublist2 in sublist1:
        flat.extend(sublist2)
print(flat)


# Example 5
a = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
b = [x for x in a if x > 4 if x % 2 == 0]
c = [x for x in a if x > 4 and x % 2 == 0]
print(b)
print(c)
assert b and c
assert b == c


# Example 6
matrix = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
filtered = [[x for x in row if x % 3 == 0]
            for row in matrix if sum(row) >= 10]
print(filtered)