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import itertools

# Linking iterators together

# chain: Combines multiple iterators into a single sequential iterator.
# cycle: Repeats an iterator’s items forever.
# tee: Splits a single iterator into multiple parallel iterators.
# zip_longest: A variant of the zip built-in function that works well with iterators of different lengths.

# Filtering items from an iterator

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# heaps in standard list types with functions like heappush, heappop, and nsmallest

# Items are always removed by highest priority (lowest number) first.
a = []
heappush(a, 5)
heappush(a, 3)
heappush(a, 7)
heappush(a, 4)

# print(heappop(a), heappop(a), heappop(a), heappop(a))

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# Double-ended Queue
fifo = collections.deque()
fifo.append(1)      # Producer
x = fifo.popleft()  # Consumer

# OrderedDict

a = OrderedDict()
a[‘foo’] = 1
a[‘bar’] = 2

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from datetime import datetime, timezone

# Conversion to computer local time
now = datetime(2014, 8, 10, 18, 18, 30)
now_utc = now.replace(tzinfo=timezone.utc)
now_local = now_utc.astimezone()
print(now_local)

# Conversion local to Unix timestamp in UTC
time_str = '2014-08-10 11:18:30'

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@contextmanager
def debug_logging(level):
    """ Change the logging level
    """
    logger = logging.getLogger()
    old_level = logger.getEffectiveLevel()
    logger.setLevel(level)
    try:
        yield

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def trace_decorator(func):
    
    @wraps(func)
    def wrapper(*args, **kwargs):
        # Decorate before
        print('Hello')
        
        # Call function
        result = func(*args, **kwargs)
        

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def gcd(pair):
    a, b = pair
    low = min(a, b)
    for i in range(low, 0, -1):
        if a % i == 0 and b % i == 0:
            return i
        
# No parallel
numbers = [(1963309, 2265973), (2030677, 3814172),
              (1551645, 2229620), (2039045, 2020802)]

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# Corutines

# Extension of generators
# They serve like "microservices"

def my_corutine():
    while True: # Alive microservice
        received_value = yield # This will freeze the corutine until a value is "send" to it
        # Do amazing work
        print("Job done with input", received_value)

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class LockingCounter(object):
    def __init__(self):
        self.lock = Lock()
        self.count = 0
    def increment(self, offset):
        with self.lock:
            self.count += offset
        
def worker(sensor_index, how_many, counter):
    for _ in range(how_many):

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def run_openssl(data):
    env = os.environ.copy()
    env[‘password’] = b’\xe24U\n\xd0Ql3S\x11’
    proc = subprocess.Popen(
        [‘openssl’, ‘enc’, ‘-des3’, ‘-pass’, ‘env:password’],
        env=env,
        stdin=subprocess.PIPE,
        stdout=subprocess.PIPE)
    proc.stdin.write(data)
    proc.stdin.flush()  # Ensure the child gets input