这一节的Homework不难，而且四道题，删成两道题目了。第二道题目的话，没有想出来。后来想了一下，其实挺简单的；错误示范我也放在这里面了
Q1: Product
这一题,其实就是对于参数n采取什么策略的意思;题目不难
def product(n, term):
"""Return the product of the first n terms in a sequence.
n: a positive integer
term: a function that takes one argument to produce the term
>>> product(3, identity) # 1 * 2 * 3
6
>>> product(5, identity) # 1 * 2 * 3 * 4 * 5
120
>>> product(3, square) # 1^2 * 2^2 * 3^2
36
>>> product(5, square) # 1^2 * 2^2 * 3^2 * 4^2 * 5^2
14400
>>> product(3, increment) # (1+1) * (2+1) * (3+1)
24
>>> product(3, triple) # 1*3 * 2*3 * 3*3
162
"""
"*** YOUR CODE HERE ***"
# 傻了，啥玩意*0不都是等于0 嘛
result = 1
while n:
result *= term(n)
n -= 1
return result
Q2: Accumulate
这一题是前面一题的进一步,我们把方法抽象出来形成一个函数,然后通过这个函数,来返回具体数据;
这一题,第一个需要考虑,merge的执行流程.我们需要考虑循环的时候,merge函数的最终结果;
👱♀ 举个例子;
accumulate(add,0,5,identify)
我们可以知道,应该是 0 + (1+2+3+4+5) 我们需要循环执行获取1-5的最终结果.所以需要一个循环;这个循环采用的是identify方法,也就是 while n: identify(5)
但是我们需要将前一个结果和后一个结果相加,那么就导致一个现象,我们需要用到add方法了.所以我们add方法需要包含在循环里面,所以应该是while n: add(0,identify(5))
还需要考虑一点,就是我们不能使用+= 而使用赋值运算符,因为add 也就是merger函数,是包含了前面的结果的;
def accumulate(merger, start, n, term):
"""Return the result of merging the first n terms in a sequence and start.
The terms to be merged are term(1), term(2), ..., term(n). merger is a
two-argument commutative function.
>>> accumulate(add, 0, 5, identity) # 0 + 1 + 2 + 3 + 4 + 5
15
>>> accumulate(add, 11, 5, identity) # 11 + 1 + 2 + 3 + 4 + 5
26
>>> accumulate(add, 11, 0, identity) # 11
11
>>> accumulate(add, 11, 3, square) # 11 + 1^2 + 2^2 + 3^2
25
>>> accumulate(mul, 2, 3, square) # 2 * 1^2 * 2^2 * 3^2
72
>>> # 2 + (1^2 + 1) + (2^2 + 1) + (3^2 + 1)
>>> accumulate(lambda x, y: x + y + 1, 2, 3, square)
19
>>> # ((2 * 1^2 * 2) * 2^2 * 2) * 3^2 * 2
>>> accumulate(lambda x, y: 2 * x * y, 2, 3, square)
576
>>> accumulate(lambda x, y: (x + y) % 17, 19, 20, square)
16
"""
"*** YOUR CODE HERE ***"
sum_total = start
while n:
sum_total = merger(sum_total, term(n))
n -= 1
return sum_total
沿用这个就行了,但是Ok对于报错页面返回有问题;直接贴结果了
Q3 product_using_accumulate
def product_using_accumulate(n, term):
"""Returns the product: term(1) * ... * term(n), using accumulate.
>>> product_using_accumulate(4, square)
576
>>> product_using_accumulate(6, triple)
524880
>>> # You aren't expected to understand the code of this test.
>>> # Check that the bodies of the functions are just return statements.
>>> # If this errors, make sure you have removed the "***YOUR CODE HERE***".
>>> import inspect, ast
>>> [type(x).__name__ for x in ast.parse(inspect.getsource(product_using_accumulate)).body[0].body]
['Expr', 'Return']
"""
"*** YOUR CODE HERE ***"
return accumulate(mul, 1, n, term)
Q4 summation_using_accumulate
def summation_using_accumulate(n, term):
"""Returns the sum: term(0) + ... + term(n), using accumulate.
>>> summation_using_accumulate(5, square)
55
>>> summation_using_accumulate(5, triple)
45
>>> # You aren't expected to understand the code of this test.
>>> # Check that the bodies of the functions are just return statements.
>>> # If this errors, make sure you have removed the "***YOUR CODE HERE***".
>>> import inspect, ast
>>> [type(x).__name__ for x in ast.parse(inspect.getsource(summation_using_accumulate)).body[0].body]
['Expr', 'Return']
"""
"*** YOUR CODE HERE ***"
return accumulate(add, 0, n, term)
最后
贴截图,结束
