面试准备

值传递和参数传递

>>> a=5
>>> '%.*s' % (a,'fang jia xin')
'fang '
>>> a = 6>>> b = (a,'fang jia xin')>>> '%.*s' % b'fang j'>>> a = 7>>> b(6, 'fang jia xin')

元组的变量传递，是copy后值传递参数

不可变对象传递值，在函数作用域内的改变，不影响函数外变量的值；可变（mutable)对象参数传递，函数可直接更改变量

class Person:
name=[]

p1=Person()
p2=Person()
p1.name.append(1)
print p1.name  # [1]
print p2.name  # [1]
print Person.name  # [1]

类变量的传递也类似函数的参数传递

class Person(object):
name=[]
def __init__(self, xing, ming):
self.xing = xing
self.ming = ming
def __getattr__(self, name):
if name == 'fang':
print('me')

魔法方法如何重写？是否需要？

super函数的使用？

https://docs.python.org/3.5/library/functions.html?highlight=super#super

getter、setter的使用？

迭代器和生成器

In Python 2.6 and higher, the best way to implement an iterator is generally to use the appropriate abstract base class from the collections standard library module – in Python 2.6, the code might be (remember to call the method next instead in Python 3):

import collections

class infinite23s(collections.Iterator):
def next(self): return 23

构建迭代器最好的方法，重写itertool.collections里的next方法

new & init

Use new when you need to control the creation of a new instance. Use init when you need to control initialization of a new instance.

new用来实例化一个类，init用来初始化instance

In general, you shouldn’t need to override new unless you’re subclassing an immutable type like str, int, unicode or tuple.

new的应用：singleton pattern（单例模式）

单例模式，也叫单子模式，是一种常用的软件设计模式。在应用这个模式时，单例对象的类必须保证只有一个实例存在。

@singleton
class MyClass:
#实现单例模式

factory

decorator

super

返回值：Return a proxy object that delegates method calls to a parent or sibling class of type.

pdb

从头开始

python -m pdb test.py

pdb.run(‘pdb_script.MyObj(5).go()’)

pdb.set_trace()

after failure: pdb.pm()

4.