# 刷题继续

### Question 41:

Write a program which can map() to make a list whose elements are square of elements in [1,2,3,4,5,6,7,8,9,10].

#### 解法一

```lst=[i for i in range(1,11)]
lst_square = list(map(lambda x:x*x,lst))
print(lst_square)```

#### 解法二

```li = [1,2,3,4,5,6,7,8,9,10]
squaredNumbers = map(lambda x: x**2, li)
print(list(squaredNumbers))```

### Question 42:

Write a program which can map() and filter() to make a list whose elements are square of even number in [1,2,3,4,5,6,7,8,9,10].

#### 解法一

```lst=[i for i in range(1,11)]
even_numbers = list(map(lambda x: x**2, filter(lambda x: x%2==0, lst)))
print(even_numbers)```

#### 解法二

```def even(x):
return x%2==0

def squer(x):
return x*x

li = [1,2,3,4,5,6,7,8,9,10]
li = map(squer,filter(even,li))
print(list(li))```

### Question 43:

Write a program which can filter() to make a list whose elements are even number between 1 and 20 (both included).

#### 解法一

```even_numbers = list(filter(lambda x: x%2==0, range(1,21)))
print(even_numbers)```

#### 解法二

```def even(x):
return x%2==0

evenNumbers = filter(even, range(1,21))
print(list(evenNumbers))```

### Question 44:

Write a program which can map() to make a list whose elements are square of numbers between 1 and 20 (both included).

#### 解法一

```def sqr(x):
return x*x

squaredNumbers = list(map(sqr, range(1,21)))
print (squaredNumbers)```

#### 解法二

```squaredNumbers = list(map(lambda x: x**2, range(1,21)))
print(squaredNumbers)```

### Question 45:

Define a class named American which has a static method called printNationality.

#### 解法一

```class American():
@staticmethod
def printNationality():
print("I am American")

american = American()
american.printNationality()   # this will not run if @staticmethod does not decorates the function.Because the class has no instance.

American.printNationality()   # this will run even though the @staticmethod does not decorate printNationality()                            ```

### Question 46:

Define a class named American and its subclass NewYorker.

#### 解法一

```class American():
pass

class NewYorker(American):
pass

american = American()
newyorker = NewYorker()

print(american)
print(newyorker)```

### Question 47:

Define a class named Circle which can be constructed by a radius. The Circle class has a method which can compute the area.

#### 解法一

```class Circle:
def area(self):

# Test
circle = Circle(5)
print(circle.area())```

### Question 48:

Define a class named Rectangle which can be constructed by a length and width. The Rectangle class has a method which can compute the area.

#### 解法一

```class Rectangle():
def __init__(self,l,w):
self.length = l
self.width = w

def area(self):
return self.length*self.width

rect = Rectangle(2,4)
print(rect.area())```

### Question 49:

Define a class named Shape and its subclass Square. The Square class has an init function which takes a length as argument. Both classes have a area function which can print the area of the shape where Shape's area is 0 by default.

#### 解法一

```class Shape():
def __init__(self):
pass

def area(self):
return 0

class Square(Shape):
def __init__(self,length = 0):
Shape.__init__(self)
self.length = length

def area(self):
return self.length*self.length

Asqr = Square(5)
print(Asqr.area())      # prints 25
print(Square().area())  # prints à```

### Question 50:

#### 解法一

`raise RuntimeError('something wrong')`

# 源代码下载

• raw_input()在Python3中是input()
• print需要加括号
• fstring可以换成.format(),或者%s，%d

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