effectivepython/example_code/item_17.py at master · AISTLAB/effectivepython · GitHub

History

executable file

138 lines (106 loc) · 2.97 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

#!/usr/bin/env 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.

# Preamble to mimick book environment

import logging

from pprint import pprint

from sys import stdout as STDOUT

# 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)

# 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 = list(numbers) # Copy the iterator

total = sum(numbers)

result = []

for value in numbers:

percent = 100 * value / total

result.append(percent)

return result

# Example 7

it = read_visits('my_numbers.txt')

percentages = normalize_copy(it)

print(percentages)

# 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

percentages = normalize_func(lambda: read_visits(path))

print(percentages)

# Example 10

class ReadVisits(object):

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)

# Example 12

def normalize_defensive(numbers):

if iter(numbers) is iter(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

# Example 13

visits = [15, 35, 80]

normalize_defensive(visits) # No error

visits = ReadVisits(path)

normalize_defensive(visits) # No error

# Example 14

try:

it = iter(visits)

normalize_defensive(it)

except:

logging.exception('Expected')

else:

assert False

effectivepython/example_code/item_17.py at master · AISTLAB/effectivepython · GitHub

Expand file tree

Breadcrumbs

item_17.py

Latest commit

History

Breadcrumbs

item_17.py

File metadata and controls