effectivepython/example_code/item_31.py at master · sharc007/effectivepython · GitHub

History

executable file

209 lines (163 loc) · 4.42 KB

Raw

100

101

102

103

104

105

106

107

108

109

110

111

112

113

114

115

116

117

118

119

120

121

122

123

124

125

126

127

128

129

130

131

132

133

134

135

136

137

138

139

140

141

142

143

144

145

146

147

148

149

150

151

152

153

154

155

156

157

158

159

160

161

162

163

164

165

166

167

168

169

170

171

172

173

174

175

176

177

178

179

180

181

182

183

184

185

186

187

188

189

190

191

192

193

194

195

196

197

198

199

200

201

202

203

204

205

206

207

208

209

#!/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

def normalize(numbers):

total = sum(numbers)

result = []

for value in numbers:

percent = 100 * value / total

result.append(percent)

return result

# Example 2

visits = [15, 35, 80]

percentages = normalize(visits)

print(percentages)

assert sum(percentages) == 100.0

# Example 3

path = 'my_numbers.txt'

with open(path, 'w') as f:

for i in (15, 35, 80):

f.write('%d\n' % i)

def read_visits(data_path):

with open(data_path) as f:

for line in f:

yield int(line)

# Example 4

it = read_visits('my_numbers.txt')

percentages = normalize(it)

print(percentages)

# Example 5

it = read_visits('my_numbers.txt')

print(list(it))

print(list(it)) # Already exhausted

# Example 6

def normalize_copy(numbers):

numbers_copy = list(numbers) # Copy the iterator

total = sum(numbers_copy)

result = []

for value in numbers_copy:

percent = 100 * value / total

result.append(percent)

return result

# Example 7

it = read_visits('my_numbers.txt')

percentages = normalize_copy(it)

print(percentages)

assert sum(percentages) == 100.0

# Example 8

def normalize_func(get_iter):

total = sum(get_iter()) # New iterator

result = []

for value in get_iter(): # New iterator

percent = 100 * value / total

result.append(percent)

return result

# Example 9

path = 'my_numbers.txt'

percentages = normalize_func(lambda: read_visits(path))

print(percentages)

assert sum(percentages) == 100.0

# Example 10

class ReadVisits:

def __init__(self, data_path):

self.data_path = data_path

def __iter__(self):

with open(self.data_path) as f:

for line in f:

yield int(line)

# Example 11

visits = ReadVisits(path)

percentages = normalize(visits)

print(percentages)

assert sum(percentages) == 100.0

# Example 12

def normalize_defensive(numbers):

if iter(numbers) is numbers: # An iterator -- bad!

raise TypeError('Must supply a container')

total = sum(numbers)

result = []

for value in numbers:

percent = 100 * value / total

result.append(percent)

return result

visits = [15, 35, 80]

normalize_defensive(visits) # No error

it = iter(visits)

try:

normalize_defensive(it)

except TypeError:

pass

else:

assert False

# Example 13

from collections.abc import Iterator

def normalize_defensive(numbers):

if isinstance(numbers, Iterator): # Another way to check

raise TypeError('Must supply a container')

total = sum(numbers)

result = []

for value in numbers:

percent = 100 * value / total

result.append(percent)

return result

visits = [15, 35, 80]

normalize_defensive(visits) # No error

it = iter(visits)

try:

normalize_defensive(it)

except TypeError:

pass

else:

assert False

# Example 14

visits = [15, 35, 80]

percentages = normalize_defensive(visits)

assert sum(percentages) == 100.0

visits = ReadVisits(path)

percentages = normalize_defensive(visits)

assert sum(percentages) == 100.0

# Example 15

try:

visits = [15, 35, 80]

it = iter(visits)

normalize_defensive(it)

except:

logging.exception('Expected')

else:

assert False

effectivepython/example_code/item_31.py at master · sharc007/effectivepython · GitHub

Expand file tree

Breadcrumbs

item_31.py

Latest commit

History

Breadcrumbs

item_31.py

File metadata and controls