Python中表達式和語句及for、while循環練習

1)表達式

常用的表達式操作符：x + y, x - yx * y, x / y, x // y, x % y邏輯運算：x or y, x and y, not x成員關系運算：x in y, x not in y對象實例測試：x is y, x not is y比較運算：x < y, x > y, x <= y, x >= y, x == y, x != y位運算：x | y, x & y, x ^ y, x << y, x >> y一元運算：-x, +x, ~x:冪運算：x ** y索引和分片：x[i], x[i:j], x[i:j:stride]調用：x(...)取屬性：  x.attribute元組：(...)序列：[...]字典：{...}三元選擇表達式：x if y else z匿名函數：lambda args: expression生成器函數發送協議：yield x 運算優先級：(...), [...], {...}s[i], s[i:j]s.attributes(...)+x, -x, ~xx ** y*, /, //, %+, -<<, >> &^|<, <=, >, >=, ==, !=is, not isin, not innotandorlambda 

2)語句：

賦值語句  調用  print： 打印對象  if/elif/else: 條件判斷  for/else: 序列迭代  while/else: 普通循環  pass: 占位符  break:   continue  def  return  yield  global: 命名空間  raise: 觸發異常  import:   from: 模塊屬性訪問  class: 類  try/except/finally: 捕捉異常  del: 刪除引用  assert: 調試檢查  with/as: 環境管理器  賦值語句：  隱式賦值：import, from, def, class, for, 函數參數  元組和列表分解賦值：當賦值符號(=)的左側為元組或列表時，Python會按照位置把右邊的對象和左邊的目標自左而右逐一進行配對兒；個數不同時會觸發異常，此時可以切片的方式進行；  多重目標賦值  增強賦值: +=, -=, *=, /=, //=, %=, 

3)for循環練習

練習1：逐一分開顯示指定字典d1中的所有元素，類似如下k1 v1k2 v2...    >>> d1 = { 'x':1,'y':2,'z':3,'m':4 }  >>> for (k,v) in d1.items():  print k,v   y 2  x 1  z 3  m 4    練習2：逐一顯示列表中l1=["Sun","Mon","Tue","Wed","Thu","Fri","Sat"]中的索引為奇數的元素；    >>> l1 = ["Sun","Mon","Tue","Wed","Thu","Fri","Sat"]  >>> for i in range(1,len(l1),2):  print l1[i]    Mon  Wed  Fri    練習3：將屬于列表l1=["Sun","Mon","Tue","Wed","Thu","Fri","Sat"]，但不屬于列表l2=["Sun","Mon","Tue","Thu","Sat"]的所有元素定義為一個新列表l3;     >>> l1 = ["Sun","Mon","Tue","Wed","Thu","Fri","Sat"]  >>> l2 = ["Sun","Mon","Tue","Thu","Sat"]  >>> l3 = [ ]  >>> for i in l1:  if i not in l2:l3.append(i)  >>> l3  ['Wed', 'Fri']     練習4：已知列表namelist=['stu1','stu2','stu3','stu4','stu5','stu6','stu7']，刪除列表removelist=['stu3', 'stu7', 'stu9']；請將屬于removelist列表中的每個元素從namelist中移除(屬于removelist，但不屬于namelist的忽略即可)；     >>> namelist= ['stu1','stu2','stu3','stu4','stu5','stu6','stu7']  >>> removelist = ['stu3', 'stu7', 'stu9']    >>> for i in namelist:  if i in removelist :namelist.remove(i)  >>> namelist  ['stu1', 'stu2', 'stu4', 'stu5', 'stu6']