我最近需要使用 Python 2.7 解開 zip 壓縮檔並分析檔案內容。所以我寫了下面的程式。然而這個程式是有問題的。它沒有辦法列出 zip 壓縮檔裡面的檔案。為什麼呢？
#!/usr/bin/env python
import os
import shutil
import sys
import tempfile
import zipfile
def unzip(zip_file_path, out_dir):
with zipfile.ZipFile(zip_file_path) as zip_file:
zip_file.extractall(out_dir)
def list_files(path):
for base, _, filenames in os.walk …如果我們要讓一個物件持有一些資源，然後希望這個物件被回收的時候釋放它持有的資源，我們該怎麼撰寫這個類別呢？舉例來說，TemporaryDirectory 類別會在建構實例的時候，使用 tempfile.mkdtemp() 產生一個暫時資料夾。當 TemporaryDirectory 的實例死亡後，會呼叫 shutil.rmtree() 刪除對應的暫時資料夾。我們該怎麼實作 TemporaryDirectory 呢？
一個簡單的想法是定義類別的建構函式與解構函式。我們可以在 __init__() 方法（建構函式）中呼叫 tempfile.mkdtemp()；另外在 __del__() 方法（解構函式）呼叫 shutil.rmtree()：
#!/usr/bin/env python3
import shutil
import tempfile
class TemporaryDirectory(object):
def __init__(self …今天要介紹 Python 3 引入的 raise ... from ... 述句。相信大家都知道 raise 述句是用來拋出一個例外。那 raise ... from ... 述句有何不同呢？
#!/usr/bin/env python3
import traceback
class TestError(ValueError):
pass
def test(buf):
try:
return (buf[2], buf[3])
except IndexError as e:
raise TestError() from e
try:
test(b'')
except Exception as e:
print('cause …from collections import defaultdict
class PrintDict(defaultdict):
def __getitem__(self, key):
print('getitem:', 'before:', key)
value = super().__getitem__(key)
print('getitem:', 'after:', key, value)
return value
def __contains__(self, key):
print('contains:', 'before:', key)
value = super().__contains__(key)
print('contains:', 'after:', key, value)
return value
def __setitem__(self, key, value …from collections import defaultdict
from itertools import repeat
import re
input_data = '''
Beautiful is better than ugly.
Explicit is better than implicit.
Simple is better than complex.
Complex is better than complicated.'''
word_freq = defaultdict(repeat(0).__next__)
for word in re.findall('\\w+', input_data):
word_freq[word.lower()] += 1
freq_words = defaultdict(list …import re
input_data = '''
Beautiful is better than ugly.
Explicit is better than implicit.
Simple is better than complex.
Complex is better than complicated.'''
word_freq = dict()
for word in re.findall('\\w+', input_data):
word_freq.setdefault(word.lower(), 0)
word_freq[word.lower()] += 1
freq_words = dict()
for word, freq in word_freq.items():
freq_words …from collections import namedtuple
Person = namedtuple('Person', ('id', 'role', 'name'))
print(Person)
people = [
Person(1, 'Research', 'Ada Lovelace'),
Person(2, 'Scientist', 'Grace Hopper'),
Person._make((3, 'Poet', 'Emily Dickinson')),
Person._make([4, 'Biologist', 'Rachel Carson']),
]
for p in people:
print('R:', p)
print('P:', p.id, p.role, p.name …class A(object):
def __init__(self, x):
self.x = x
def _get_y(self):
return self.x * 2
y = property(_get_y)
def _get_z(self):
return self.x * 2
def __get_z(self):
return self._get_z()
z = property(__get_z)
class B(A):
def _get_y(self):
return self.x * 3
#y = property(_get_y)
def …class Action(object):
def __init__(self, name):
self.name = name
def __call__(self, *args, **kwargs):
print(self.name, *args, **kwargs)
actions = [
Action('Hello'),
Action('Bonjour'),
Action('Goodbye'),
]
for action in actions:
action('world')
class EventHandler(object):
def __init__(self, name):
self.name = name
def test1(self, *args, **kwargs):
print('test1:', self.name, *args, **kwargs)
def test2(self, *args, **kwargs):
print('test2:', self.name, *args, **kwargs)
# test3() is a normal function, not enclosed by class statement.
def test3(self, *args, **kwargs):
print('test3:', self …Page 1 / 4 Next »
