effectivepython/example_code/item_37.py at master · sharc007/effectivepython · GitHub

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#!/usr/bin/env PYTHONHASHSEED=1234 python3

# 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

class SimpleGradebook:

def __init__(self):

self._grades = {}

def add_student(self, name):

self._grades[name] = []

def report_grade(self, name, score):

self._grades[name].append(score)

def average_grade(self, name):

grades = self._grades[name]

return sum(grades) / len(grades)

# Example 2

book = SimpleGradebook()

book.add_student('Isaac Newton')

book.report_grade('Isaac Newton', 90)

book.report_grade('Isaac Newton', 95)

book.report_grade('Isaac Newton', 85)

print(book.average_grade('Isaac Newton'))

# Example 3

from collections import defaultdict

class BySubjectGradebook:

def __init__(self):

self._grades = {} # Outer dict

def add_student(self, name):

self._grades[name] = defaultdict(list) # Inner dict

# Example 4

def report_grade(self, name, subject, grade):

by_subject = self._grades[name]

grade_list = by_subject[subject]

grade_list.append(grade)

def average_grade(self, name):

by_subject = self._grades[name]

total, count = 0, 0

for grades in by_subject.values():

total += sum(grades)

count += len(grades)

return total / count

# Example 5

book = BySubjectGradebook()

book.add_student('Albert Einstein')

book.report_grade('Albert Einstein', 'Math', 75)

book.report_grade('Albert Einstein', 'Math', 65)

book.report_grade('Albert Einstein', 'Gym', 90)

book.report_grade('Albert Einstein', 'Gym', 95)

print(book.average_grade('Albert Einstein'))

# Example 6

class WeightedGradebook:

def __init__(self):

self._grades = {}

def add_student(self, name):

self._grades[name] = defaultdict(list)

def report_grade(self, name, subject, score, weight):

by_subject = self._grades[name]

grade_list = by_subject[subject]

grade_list.append((score, weight))

# Example 7

def average_grade(self, name):

by_subject = self._grades[name]

score_sum, score_count = 0, 0

for subject, scores in by_subject.items():

subject_avg, total_weight = 0, 0

for score, weight in scores:

subject_avg += score * weight

total_weight += weight

score_sum += subject_avg / total_weight

score_count += 1

return score_sum / score_count

# Example 8

book = WeightedGradebook()

book.add_student('Albert Einstein')

book.report_grade('Albert Einstein', 'Math', 75, 0.05)

book.report_grade('Albert Einstein', 'Math', 65, 0.15)

book.report_grade('Albert Einstein', 'Math', 70, 0.80)

book.report_grade('Albert Einstein', 'Gym', 100, 0.40)

book.report_grade('Albert Einstein', 'Gym', 85, 0.60)

print(book.average_grade('Albert Einstein'))

# Example 9

grades = []

grades.append((95, 0.45))

grades.append((85, 0.55))

total = sum(score * weight for score, weight in grades)

total_weight = sum(weight for _, weight in grades)

average_grade = total / total_weight

print(average_grade)

# Example 10

grades = []

grades.append((95, 0.45, 'Great job'))

grades.append((85, 0.55, 'Better next time'))

total = sum(score * weight for score, weight, _ in grades)

total_weight = sum(weight for _, weight, _ in grades)

average_grade = total / total_weight

print(average_grade)

# Example 11

from collections import namedtuple

Grade = namedtuple('Grade', ('score', 'weight'))

# Example 12

class Subject:

def __init__(self):

self._grades = []

def report_grade(self, score, weight):

self._grades.append(Grade(score, weight))

def average_grade(self):

total, total_weight = 0, 0

for grade in self._grades:

total += grade.score * grade.weight

total_weight += grade.weight

return total / total_weight

# Example 13

class Student:

def __init__(self):

self._subjects = defaultdict(Subject)

def get_subject(self, name):

return self._subjects[name]

def average_grade(self):

total, count = 0, 0

for subject in self._subjects.values():

total += subject.average_grade()

count += 1

return total / count

# Example 14

class Gradebook:

def __init__(self):

self._students = defaultdict(Student)

def get_student(self, name):

return self._students[name]

# Example 15

book = Gradebook()

albert = book.get_student('Albert Einstein')

math = albert.get_subject('Math')

math.report_grade(75, 0.05)

math.report_grade(65, 0.15)

math.report_grade(70, 0.80)

gym = albert.get_subject('Gym')

gym.report_grade(100, 0.40)

gym.report_grade(85, 0.60)

print(albert.average_grade())

effectivepython/example_code/item_37.py at master · sharc007/effectivepython · GitHub

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