Python中表達式和語句及for、while循環練習

Python中表達式和語句及for、while循環練習

1)表達式

經常使用的表達式操做符：
        x + y, x - y
        x * y, x / y, x // y, x % y

        邏輯運算：
        x or y, x and y, not x

        成員關係運算：
        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.attribute
        s(...)
        +x, -x, ~x
        x ** y
        *, /, //, %
        +, -
        <<, >> 
        &
        ^
        |
        <, <=, >, >=, ==, !=
        is, not is
        in, not in
        not
        and
        or
        lambda

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: 佔位符
    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(=)的左側爲元組或列表時，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；個數不一樣時會觸發異常，此時能夠切片的方式進行；
        
            多重目標賦值
        
            加強賦值: +=, -=, *=, /=, //=, %=,

3)for循環練習

練習1：逐一分開顯示指定字典d1中的全部元素，相似以下
        k1 v1
        k2 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"]中的索引爲奇數的元素；
    
            >>> 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：將屬於列表l1=["Sun","Mon","Tue","Wed","Thu","Fri","Sat"]，但不屬於列表l2=["Sun","Mon","Tue","Thu","Sat"]的全部元素定義爲一個新列表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']；請將屬於removelist列表中的每一個元素從namelist中移除(屬於removelist，但不屬於namelist的忽略便可)；
     
            >>> 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']

4)while循環練習

練習1：逐一顯示指定列表中的全部元素；
        
            >>> l1 = [1,2,3,4,5]
            >>> i = 0
            >>> while i < len(l1)
                    print l1[i]
                    i += 1
            
            1
            2
            3
            4
            5
        
            >>> l1 = [1,2,3,4,5]
            >>> while l1:                        
                    print l1.pop(0)
                    
            1
            2
            3
            4
            5
            
        練習2：求100之內全部偶數之和；
            
            >>> i = 0
            >>> sum = 0 
            >>> while i < 101:
                    sum += i
                    i += 2
                print sum
            
            2550
            
            >>>  for i in range(0,101,2):
                    sum+=i   
                 print sum
            
            2550
            
       練習3：逐一顯示指定字典的全部鍵；並於顯示結束後說明總鍵數；
       
            >>> d1 = {'x':1, 'y':23, 'z': 78}
            >>> i1 = d1.keys()
            >>> while i1:
                    print i1.pop(0)
                else:
                    print len(d1)
            x
            y
            z
            3        

       練習4：建立一個包含了100之內全部奇數的列表；
       
            >>> d1 = [ ]
            >>> i = 1
            >>> while i < 101:
                    d1.append(i)
                    i+=2
            >>> print d1
            [1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, 43, 45, 47, 49, 51, 53, 55, 57, 59, 61, 63, 65, 67, 69, 71, 73, 75, 77, 79, 81, 83, 85, 87, 89, 91, 93, 95, 97, 99]    
           
           >>> d1 = [ ] 
            >>> for i in range(1,101,2)
                    d1.append(i)
            >>> print d1
            [1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, 43, 45, 47, 49, 51, 53, 55, 57, 59, 61, 63, 65, 67, 69, 71, 73, 75, 77, 79, 81, 83, 85, 87, 89, 91, 93, 95, 97, 99]
            
        練習5：列表l1=[0,1,2,3,4,5,6], 列表l2=["Sun","Mon","Tue","Wed","Thu","Fri","Sat"]，以第一個列表中的元素爲鍵，以第二個列表中的元素爲值生成字典d1；
             
            >>> l1 = [0,1,2,3,4,5,6] 
            >>> l2 = ["Sun","Mon","Tue","Wed","Thu","Fri","Sat"]
            >>> d1 = {}
            >>> count = 0
            >>> if len(l1) == len(l2):
                    while count < len(l1):
                        d1[l1[count]] = l2[count] 
                        count += 1