《Python基础教程》一点笔记

这本书还是月初的时候翻了翻，看了前十章左右就发现这本书写的比较烂，翻译地就更烂了，讲的内容其实没有抓住重点。

下面是看的时候记得几小段代码：

 #首字母相同的男生女生
 girls = ['alice', 'bernice', 'clarice']
 boys = ['chris', 'arnold', 'bob']
 lettergirls = {}
 for girl in girls:
     lettergirls.setdefault(girl[0], []).append(girl)
 print([b+'+'+ｇ for b in boys for g in lettergirls[b[0]]])

 #斐波那契数列
 def fibs(num):
     result = [1, 2]
     for i in range(num - 2):
         result.append(result[-2] + result[-1])
     return result
 print(fibs(20))

 #存储全名的字典
 def init(data):
     data['first'] = {}
     data['middle'] = {}
     data['last'] = {}
 def lookup(data, label, name):
     return data[label].get(name)
 def store(data, full_name):
     names = full_name.split()
     if len(names) == 2:
         names.insert(1, ' ')
     labels = ('first', 'middle', 'last')
     for label, name = zip(labels, names):
         people = lookup(data, label, name)
         if people:
             people.append(full_name)
         else:
             data[label][name] = [full_name]

 #递归经典：阶乘、幂、二分查找
 def search(sequence, number, lower, upper):
     if lower == upper:
         assert number == sequence[upper]
         return upper
     else:
         middle = (lower + upper) // 2
         if number > sequence[middle]:
             return search(sequence, number, middle + 1, upper)
         else:
             return search(sequence, number, lower, middle)

 #模拟实现无穷算术序列
 def checkIndex(key):
     if not isinstance(key, (int, long)):
         raise TypeError
     if key < 0:
         raise IndexError
 class ArithmeticSequence:
     def __init__(self, start = 0, step = 1):
         self.start = start
         self.step = step
         self.changed = {}
     def __getitem__(self, key):
         checkIndex(key)
         try:
             return self.changed[key]
         except KeyError:
             return self.start + key * self.step
     def __setitem__(self, key, value):
         checkIndex(key)
         self.changed[key] = value

 #基本的序列与映射规则
 def checkIndex(key):
     if not isinstance(key, (int, long)):
         raise TypeError
     if key < 0:
         raise IndexError
 class ArithmeticSequence:
     def __init__(self, start = 0, step = 1):
         self.start = start
         self.step = step
         self.changed = {}
     def __getitem__(self, key):
         checkIndex(key)
         try:
             return self.changed[key]
         except KeyError:
             return self.start + key * self.step
     def __setitem__(self, key, value):
         checkIndex(key)
         self.changed[key] = value
 #带有访问计数的列表
 class CounterList(list):
     def __init__(self, *agrs):
         super(CounterList, self).__init__(*args)
         self.counter = 0
     def __getitem__(self, index):
         self.counter += 1
         return super(CounterList, self).__getitem__(index)