举例讲解Python常用模块

from datetime import datetime as dt
dt.utcnow() # 系统UTC时间
dt.now() # 系统当前时间
dt(2018, 3, 27, 14, 30) # 获得2018-3-27 14:30对应的datetime对象
dt.now().timestamp() # 秒数1522133962.527885
dt.fromtimestamp(1522133962.527885) # 从秒到datetime对象
dt.strptime('2015-6-1 18:19:59', '%Y-%m-%d %H:%M:%S') # string转datetime对象
dt.now().strftime('%a, %b %d %H:%M') # datetime转string

from collections import namedtuple
Point = namedtuple('Point', ['x', 'y', 'z'])
p = Point(1, 1, 1)
p.x # 1
p.z # 1
p.x = 2 # Error

from collections import deque
q = deque(['a', 'b', 'c'])
q.append('x')
q.pop() # x
q.append('u')
q.popleft() # a

from collections import defaultdict
dd = defaultdict(lambda : None)
dd['x'] = 1
dd['x'] # 1
print(dd['y']) # None

from collections import OrderedDict
od = OrderedDict()
od['x'] = 1
od['y'] = 2
od['z'] = 3
for item in od:
  print(item) # x y z

from collections import Counter
c = Counter()
c['x'] # 0
c['x'] = 'x'
c['x'] # x

import base64
base64.b64encode(b'hello') # b'aGVsbG8='
base64.b64decode(b'aGVsbG8=') # b'hello'

import hashlib as hash
md5 = hash.md5()
md5.update('233'.encode('utf-8'))
print(md5.hexdigest()) # e165421110ba03099a1c0393373c5b43

import hmac
password = b'888888'
salt = b'abc'
h = hmac.new(salt, password, digestmod='MD5')
h.hexdigest() # 519151ad14e431254ff684cf4dba2d39

import itertools
n = 0
for item in itertools.count(1):
  print(item) # 1, 2 ... 10
  n += 1
  if n > 10:
    break
n = 0
for item in itertools.cycle('ABC'):
  print(item) # A, B, C, A ...
  n += 1
  if n > 10:
    break
n = 0
for item in itertools.repeat('A'):
  print(item) # A, A, A ...
  n += 1
  if n > 10:
    break
# 组合多个可迭代对象
for item in itertools.chain('ABC', 'XYZ'):
  print(item) # A, B, C, X, Y, Z

from contextlib import contextmanager
@contextmanager
def withable(name):
  yield name
  print('end')
with withable('x') as res:
  print(res) # x, end

from urllib import request
with request.urlopen('https://amsimple.com') as res:
  data = res.read()
  print('Status:', res.status, res.reason)
  for k, v in res.getheaders():
    print('%s: %s' % (k, v))