ZhouYang1993

import re
re.match(r'\d{5}','12345')
# <_sre.SRE_Match object; span=(0, 5), match='12345'>
re.match(r'\d{5}','1234')
# None

ZhouYang1993

>>> 'a b   c'.split(' ')
# ['a', 'b', '', '', 'c'] Can't split by consecutive spaces.

>>> re.split(r'\s+', 'a b   c')
# ['a', 'b', 'c']

>>> re.split(r'[\s\,]+', 'a,b, c  d')
# ['a', 'b', 'c', 'd']

>>> re.split(r'[\s\,\;]+', 'a,b;; c  d')

ZhouYang1993

time='18:05'
matched = re.match(r'^(0[0-9]|1[0-9]|2[0-3])\:(0[0-9]|1[0-9]|2[0-9]|3[0-9]|4[0-9]|5[0-9])$', time)
matched.groups()
# ('18', '05') show all groups(substrings)
matched.group()
# '18:05' group will always be the original string
matched.group(0)
# '18:05' group(0) will always be the original string
matched.group(1)
# '18'

ZhouYang1993

time='18:05'
matched = re.match(r'^(0[0-9]|1[0-9]|2[0-3])\:(0[0-9]|1[0-9]|2[0-9]|3[0-9]|4[0-9]|5[0-9])$', time)
matched.groups()
# ('18', '05')
matched.group()
# '18:05' 
matched.group(0)
# '18:05' group(0) returns the original string
matched.group(1)
# '18'

ZhouYang1993

import re
re_three_numbers = re.compile(r'^\d{3}$')
re_three_numbers.match('123')
# <_sre.SRE_Match object; span=(0, 3), match='123'>
re_three_numbers.match('12345')
# None

ZhouYang1993

class MyClass(object):
    class_attr = 1

    def __init__(self, value):
        self.instance_attr = value

ZhouYang1993

class MyClass(object):
     class_attr = 0
     def __init__(self, instance_attr):
      self.instance_attr = instance_attr
        
MyClass.class_attr
# 0
MyClass.instace_attr
# Traceback (most recent call last):
#   File "/usr/lib/python3.6/code.py", line 91, in runcode

ZhouYang1993

class MyClass(object):
    class_attr = 0

    def __init__(self, instance_attr):
        self.instance_attr = instance_attr
print(MyClass.__dict__)
# {'__module__': '__main__', 'class_attr': 0, '__init__': <function MyClass.__init__ at 0x7f00cb7fcea0>, '__dict__': <attribute '__dict__' of 'MyClass' objects>, '__weakref__': <attribute '__weakref__' of 'MyClass' objects>, '__doc__': None}
my_instance = MyClass(1)
print(my_instance.__dict__)
# {'instance_attr': 1}

ZhouYang1993

class HandsomeGuy(object):
     name = 'Yang'
     def __init__(self, value):
        self.name = value
         
guy = HandsomeGuy('Jack')
HandsomeGuy.name
# 'Yang'
guy.name
# 'Jack'

ZhouYang1993

class MyClass(object):
  data = 0

  def __init__(self, value):
    self.instance_data = value
        
MyClass.data
# 0
my_instance = MyClass(3)
my_instance.data