Python Cookbook 学习笔记 可以拿来和面试官吹牛用

仅仅是Python Cookbook的代码而已，自己在看这书中觉得感兴趣的代码。

可以直接保存为py文件运行

# -*- coding: utf-8 -*-
#coding=utf-8
#################################################
print "复制一个对象副本"
import copy
a = [1, 2, 3, 4, 5, 6]
b = copy.copy(a)
###################################################
print "若列表中元素存在则返回之"
def list_get(L, i, v=None):
    if - len(L) <= i < len(L):
        return L[i]
    else:
        return v
#print "Input a List\n"
#L = raw_input('>')
#L = L.split(',')
#print "Input a Index\n"
#i = raw_input('>')
#i = int(i)
#a = list_get(L, i)
#print "a is %s" % a
#print "Bye"
####################################################
print "循环访问序列中的索引和元素"
def change_item(L):
    '''L is a list'''
    for index, item in enumerate(L):
        print index,item
        if item > 23:
            L[index] = item - 1
change_item(a)         
######################################################
print "创建一个10 x 5阵列"  
multilist = [[0 for col in range(5)] for row in range(10)]
print multilist
for row in range(10):
    for col in range(5):
        print "8", #加个逗号，就可以不换行
   
    print
#####################################################
'''
x=[1,2,3],y=['a','b','c']
zip(x,y)
[(1,'a'),(2,'b'),(3,'c')]
zip函数接受任意多个序列作为参数，将所有序列按相同的索引组合成一个元素是各个序列合并成的tuple的新序列，
新的序列的长度以参数中最短的序列为准。
另外(*)操作符与zip函数配合可以实现与zip相反的功能，即将合并的序列拆成多个tuple
zip(*zip(x,y))
[(1,2,3),('a','b','c')]


'''

print "二维阵列变换"
array = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
print map(list, zip(*array)),array  #
#####################################################
print '从字典中取值'
a = {"b":2, "c":3, "d":4, "e":5}
print a.get('c')
print a.get("bc", "kk is a genius")
######################################################
print '在无需多引援的情况下创建字典'
data = dict(red=1, green=2, yellow=3)
print data
#######################################################
print "获取字典的一个子集"
d = {'a': 5, 'b': 6, 'c': 7}
def sub_dict(somedict, somekeys, default=None):
    return dict([ (k, somedict.get(k, default)) for k in somekeys ])
def sub_dict_remove(somedict, somekeys, default=None):
    return dict([ (k, somedict.pop(k, default)) for k in somekeys ])


def sub_dict_strict(somedict, somekeys):
    return dict([ (k, somedict[k]) for k in somekeys ])

def sub_dict_remove_strict(somedict, somekeys):
    return dict([(k,somedict.pop(k)) for k in somekeys])

def sub_dict_select(somedict, somekeys):
    return dict([ (k, somedict[k]) for k in somekeys if k in somedict])
def sub_dict_remove_select(somedict, somekeys):
    return dict([ (k, somedict.pop(k)) for k in somekeys if k in somedict])


print sub_dict(d, 'ab'), d
print sub_dict_remove(d, 'ab'), d

#print sub_dict_strict(d, 'ab'), d
#print sub_dict_remove_strict(d,'ab'),d


###########################################################
print "反转键值"
e = {'a': 5, 'b': 6, 'c': 7}
def invert_dict(e):
    return dict([ (v, k) for k, v in e.iteritems() ])

from itertools import izip
def invert_dict_fast(e):
    return dict(izip(e.itervalues(), e.iterkeys()))
print "e is", e
print invert_dict(e), e
###########################################################
print "设置默认值,setdefault 有key，返回值，若无新加【】"
key = 'black'
value = 1
d1 = {  }
d.setdefault(key, [  ]).append(value)

#############################################################
print "在保留序列顺序的前提下，消除其中的重复"
test=[3,3,3,3,2,1,1,1,5,5,4,4,5,5]
def uniquer(seq, f=None):
    #import pdb;pdb.set_trace()
    """ Keeps earliest occurring item of each f-defined equivalence class """
    if f is None:    # f's default is the identity function f(x) -> x
        def f(x): return x
    already_seen = set( )
    result = []
    for item in seq:
        marker = f(item)
        if marker not in already_seen:
            already_seen.add(marker)
            result.append(item)
    return result
print uniquer(test)
################################################################
print "记录异常信息except，写入字典"
'''
import cStringIO, traceback
def process_all_files(all_filenames, fatal_exceptions=(KeyboardInterrupt, MemoryError)):
    bad_filenames = {}
    for one_filename in all_filenames:
        try:
            process_one_file(one_filename):
        except fatal_exceptions:
            raise
        except Exception:
            f = cStringIO.StringIO()
            traceback.print_exc(file=f)
            bad_filenames[one_filename] = f.getvalue()
    return bad_filenames
'''