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item_19.py
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#!/usr/bin/env PYTHONHASHSEED=1234 python3
# Copyright 2014-2019 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.
# Reproduce book environment
import random
random.seed(1234)
import logging
from pprint import pprint
from sys import stdout as STDOUT
# Write all output to a temporary directory
import atexit
import gc
import io
import os
import tempfile
TEST_DIR = tempfile.TemporaryDirectory()
atexit.register(TEST_DIR.cleanup)
# Make sure Windows processes exit cleanly
OLD_CWD = os.getcwd()
atexit.register(lambda: os.chdir(OLD_CWD))
os.chdir(TEST_DIR.name)
def close_open_files():
everything = gc.get_objects()
for obj in everything:
if isinstance(obj, io.IOBase):
obj.close()
atexit.register(close_open_files)
# Example 1
def get_stats(numbers):#function input number output tuple (min,max)
minimum = min(numbers)
maximum = max(numbers)
return minimum, maximum
lengths = [63, 73, 72, 60, 67, 66, 71, 61, 72, 70]
# assign/unpack the return values max.min from function
# to variables
minimum, maximum = get_stats(lengths) # Two return values assign to vars
print(f"Min: {minimum}, Max: {maximum}")
# Example 2
# assign to values to two variables
first, second = 1, 2#assign 2 numbers to vars
assert first == 1
assert second == 2
def my_function():#function return to static numbers
return 1, 2
# assign two values to 2 variables through function
first, second = my_function()#assign return function to vars
assert first == 1
assert second == 2
# Example 3
# lengths = [63, 73, 72, 60, 67, 66, 71, 61, 72, 70]
# function accept list return list by list comprehension
def get_avg_ratio(numbers):
average = sum(numbers) / len(numbers)
# x divided by average to determine ratio
scaled = [x / average for x in numbers]#every number from list divide by average
# sort smal to big
scaled.sort(reverse=True)#list sort reverse and assign
return scaled
# divide/unpack list in 3 pieces 2 var and middle list
longest, *middle, shortest = get_avg_ratio(lengths)#assign parts of list to vars
print(f"Longest: {longest:>4.0%}")
print(f"Shortest: {shortest:>4.0%}")
# Example 4
def get_stats(numbers):
minimum = min(numbers)
maximum = max(numbers)
count = len(numbers)
average = sum(numbers) / count
sorted_numbers = sorted(numbers)
# floor division by 2 3.5 => 3 etc.
middle = count // 2
# define middle in even len list
# mod count divided by 2 true then middle
if count % 2 == 0:
# len is 8 lower pos 4 => 0,1,2,3
lower = sorted_numbers[middle - 1]
# len is 8/2 = 4 pos 5 => 0,1,2,3,4
upper = sorted_numbers[middle]
median = (lower + upper) / 2
else:
# middle is oneven say 7//2 = 3(floor 3.5) pos 4 0,1,2,3
median = sorted_numbers[middle]
return minimum, maximum, average, median, count
# assign 5 variables from function is positional
minimum, maximum, average, median, count = get_stats(lengths)#assign return to vars
print(f"Min: {minimum}, Max: {maximum}")
print(f"Average: {average}, Median: {median}, Count {count}")
assert minimum == 60
assert maximum == 73
assert average == 67.5
assert median == 68.5
assert count == 10
# Verify odd count median
# variables are positional dummyvariables by "_"
# _, _, _, median, count = get_stats([1, 2, 3])
_, _, _, median, count = get_stats([1, 2, 3])#assign only two of 5 vars
assert median == 2
assert count == 3
# Example 5
# Correct:
# positional names function local scop
minimum, maximum, average, median, count = get_stats(lengths)
print(f"Min: {minimum}, Max: {maximum}")
print(f"Average: {average}, Median: {median}, Count {count}")
# Oops! Median and average swapped:
minimum, maximum, median, average, count = get_stats(lengths)#assign is positional
print(f"Min: {minimum}, Max: {maximum}")
print(f"Average: {average}, Median: {median}, Count {count}")
# Example 6
# advise never unpack more than 3 items
minimum, maximum, average, median, count = get_stats(lengths)
minimum, maximum, average, median, count = get_stats(lengths)
(minimum, maximum, average, median, count) = get_stats(lengths)
(minimum, maximum, average, median, count) = get_stats(lengths)