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(gs3_9) zjr@sgd-linux-1:~/cnn_test$ asciinema rec first.cast
asciinema: recording asciicast to first.cast
asciinema: press <ctrl-d> or type "exit" when you're done
意思就是日志会被保存在当前文件夹下的first.cast，如果你想结束录制，按 Ctrl + D 即可。
# Python 实用宝典
# https://pythondict.com
def handle_argv(self, prog_name, argv, command=None):
"""Parse command-line arguments from ``argv`` and dispatch
to :meth:`run`.
:param prog_name: The program name (``argv[0]``).
:param argv: Command arguments.
Exits with an error message if :attr:`supports_args` is disabled
and ``argv`` contains positional arguments.
"""
options, args = self.prepare_args(
*self.parse_options(prog_name, argv, command))
return self(*args, **options)
Command 类的 __call__函数：
# Python 实用宝典
# https://pythondict.com
def __call__(self, *args, **kwargs):
random.seed() # maybe we were forked.
self.verify_args(args)
try:
ret = self.run(*args, **kwargs)
return ret if ret is not None else EX_OK
except self.UsageError as exc:
self.on_usage_error(exc)
return exc.status
except self.Error as exc:
self.on_error(exc)
return exc.status
# Python 实用宝典
# https://pythondict.com
def start(self, embedded_process=False, drift=-0.010):
info('beat: Starting...')
# 打印最大间隔时间
debug('beat: Ticking with max interval->%s',
humanize_seconds(self.scheduler.max_interval))
# 通知注册该signal的函数
signals.beat_init.send(sender=self)
if embedded_process:
signals.beat_embedded_init.send(sender=self)
platforms.set_process_title('celery beat')
try:
while not self._is_shutdown.is_set():
# 调用scheduler.tick()函数检查还剩多余时间
interval = self.scheduler.tick()
interval = interval + drift if interval else interval
# 如果大于0
if interval and interval > 0:
debug('beat: Waking up %s.',
humanize_seconds(interval, prefix='in '))
# 休眠
time.sleep(interval)
if self.scheduler.should_sync():
self.scheduler._do_sync()
except (KeyboardInterrupt, SystemExit):
self._is_shutdown.set()
finally:
self.sync()
这里重点看 self.scheduler.tick() 方法：
# Python 实用宝典
# https://pythondict.com
def tick(self):
"""Run a tick, that is one iteration of the scheduler.
Executes all due tasks.
"""
remaining_times = []
try:
# 遍历每个周期任务设定
for entry in values(self.schedule):
# 下次运行时间
next_time_to_run = self.maybe_due(entry, self.publisher)
if next_time_to_run:
remaining_times.append(next_time_to_run)
except RuntimeError:
pass
return min(remaining_times + [self.max_interval])
>>> def create_generator():
... mylist = range(3)
... for i in mylist:
... yield i*i
...
>>> mygenerator = create_generator() # create a generator
>>> print(mygenerator) # mygenerator is an object!
<generator object create_generator at 0xb7555c34>
>>> for i in mygenerator:
... print(i)
0
1
4
第一次 for 调用从您的函数创建的生成器对象时，它将从头开始运行您的函数中的代码，直到命中yield，然后它将返回循环的第一个值。然后，每个后续调用将运行您在函数中编写的循环的另一次迭代并返回下一个值。这将一直持续到生成器被认为是空的为止。
4. 控制生成器耗尽的一个例子
>>> class Bank(): # Let's create a bank, building ATMs
... crisis = False
... def create_atm(self):
... while not self.crisis:
... yield "$100"
>>> hsbc = Bank() # When everything's ok the ATM gives you as much as you want
>>> corner_street_atm = hsbc.create_atm()
>>> print(corner_street_atm.next())
$100
>>> print(corner_street_atm.next())
$100
>>> print([corner_street_atm.next() for cash in range(5)])
['$100', '$100', '$100', '$100', '$100']
>>> hsbc.crisis = True # Crisis is coming, no more money!
>>> print(corner_street_atm.next())
<type 'exceptions.StopIteration'>
>>> wall_street_atm = hsbc.create_atm() # It's even true for new ATMs
>>> print(wall_street_atm.next())
<type 'exceptions.StopIteration'>
>>> hsbc.crisis = False # The trouble is, even post-crisis the ATM remains empty
>>> print(corner_street_atm.next())
<type 'exceptions.StopIteration'>
>>> brand_new_atm = hsbc.create_atm() # Build a new one to get back in business
>>> for cash in brand_new_atm:
... print cash
$100
$100
$100
$100
$100
$100
$100
$100
$100
...
你可以在代码中检查 Python 的版本，以确保你的用户没有在不兼容的版本中运行脚本。检查方式如下：ifnot sys.version_info > (2, 7): # berate your user for running a 10 year # python version elifnot sys.version_info >= (3, 5): # Kindly tell your user (s)he needs to upgrade # because you’re using 3.5 features
完整的命令列表，请点击此处查看（https://ipython.readthedocs.io/en/stable/interactive/magics.html）。还有一个非常实用的功能：引用上一个命令的输出。In 和 Out 是实际的对象。你可以通过 Out[3] 的形式使用第三个命令的输出。IPython 的安装命令如下：pip3 install ipython
4.Python 编程技巧 – 列表推导式
你可以利用列表推导式，避免使用循环填充列表时的繁琐。列表推导式的基本语法如下：[ expression for item in list if conditional ]举一个基本的例子：用一组有序数字填充一个列表：mylist = [i for i in range(10)] print(mylist) # [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]由于可以使用表达式，所以你也可以做一些算术运算：squares = [x**2 for x in range(10)] print(squares) # [0, 1, 4, 9, 16, 25, 36, 49, 64, 81]甚至可以调用外部函数：defsome_function(a): return (a + 5) / 2
my_formula = [some_function(i) for i in range(10)] print(my_formula) # [2, 3, 3, 4, 4, 5, 5, 6, 6, 7]
最后，你还可以使用 ‘if’ 来过滤列表。在如下示例中，我们只保留能被2整除的数字：filtered = [i for i in range(20) if i%2==0] print(filtered) # [0, 2, 4, 6, 8, 10, 12, 14, 16, 18]
有些人非常喜欢表情符，而有些人则深恶痛绝。我在此郑重声明：在分析社交媒体数据时，表情符可以派上大用场。首先，我们来安装表情符模块：pip3 install emoji安装完成后，你可以按照如下方式使用：import emoji result = emoji.emojize(‘Python is :thumbs_up:’) print(result) # ‘Python is 👍’
# You can also reverse this: result = emoji.demojize(‘Python is 👍’) print(result) # ‘Python is :thumbs_up:’
# Convert a string representation of # a number into a list of ints. list_of_ints = list(map(int, “1234567”))) print(list_of_ints) # [1, 2, 3, 4, 5, 6, 7]
# And since a string can be treated like a # list of letters, you can also get the # unique letters from a string this way: print (set(“aaabbbcccdddeeefff”)) # {‘a’, ‘b’, ‘c’, ‘d’, ‘e’, ‘f’}
虽然你可以用三重引号将代码中的多行字符串括起来，但是这种做法并不理想。所有放在三重引号之间的内容都会成为字符串，包括代码的格式，如下所示。我更喜欢另一种方法，这种方法不仅可以将多行字符串连接在一起，而且还可以保证代码的整洁。唯一的缺点是你需要明确指定换行符。s1 = “””Multi line strings can be put between triple quotes. It’s not ideal when formatting your code though”””
print (s1) # Multi line strings can be put # between triple quotes. It’s not ideal # when formatting your code though
s2 = (“You can also concatenate multiple\n” + “strings this way, but you’ll have to\n” “explicitly put in the newlines”)
print(s2) # You can also concatenate multiple # strings this way, but you’ll have to # explicitly put in the newlines
24. Python 编程技巧 – 条件赋值中的三元运算符
这种方法可以让代码更简洁，同时又可以保证代码的可读性：[on_true] if [expression] else [on_false]示例如下：x = “Success!” if (y == 2) else“Failed!”
print(Fore.RED + ‘some red text’) print(Back.GREEN + ‘and with a green background’) print(Style.DIM + ‘and in dim text’) print(Style.RESET_ALL) print(‘back to normal now’)
DEBUG:schedule:Running *all* 1 jobs with 0s delay in between
DEBUG:schedule:Running job Job(interval=1, unit=seconds, do=job, args=(), kwargs={})
Hello, Logs
DEBUG:schedule:Deleting *all* jobs
