pYTHON again

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Pick python up from a link for new position:

type

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type(123)
isinstance(instance_name, class_name)

@property

transfer get()method in a class to a decorator

define function

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def my_abs(x):
    if not isinstance(x, (int, float)):
        raise TypeError('bad operand type')

fun decorator

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@decorator
def fun()

filter

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def is_odd(n):
	return n%2 == 1 
	
list(filter(is_odd, [1, 2, 3, 4])

lambda

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list(map(lambda x: x*2, [1, 2, 3, 4]))

slice

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L = [1, 2, 3, 4, 5]
L[-2:]  #[4, 5]

list generation

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[x*2 for x in range(1, 5)]

class & instance

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class s(object):
	def \__init__(self, name):
		self.name = name
	
	def print_s(self):
		print('%s:' %(self.name))
		
s1 = s("john")
s1.print_s()

customized class

dynamic language, so the instance of any class can be added any other attributes. 

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class s(object):
	def \__init__(self, name):
			self._name = name
	def \__str__(self):
		return 's object(name: %s)' % self._name
	
	def \__getattr__(self, attr):
		if attr == 'attr1':
			return lambda: attr1.value

raise & except

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import logging
try:
	print('try...')
	r = 10/0 
	print('result: ', r)
except ZeroDiisionError as e:
	print('except', e)
	logging.exception(e)
finally:
	print('finally..')

IO stream

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f = open('test.log', 'r')
print(f.read(size))
f.close() 
#or 
with open('test.log', 'r') as f:
	printf(f.read(size)) 
	for line in f.readlines():
		print(line.strip())

pickling

serializaion/marshalling/flattening and reverse

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import pickle
import json
d = dic(name='zj', age='18')
pickle.dumps(d)
json.dumps(d)