实验四

print(sum)
sum = 42
print(sum)

def inc(n):
    sum = n+1
    print(sum)
    return sum
 
sum = inc(7) + inc(7)
print(sum)

第一个sum,内置作用域.第二个sum变量名,第三个sum局部作用域,第四个sum全局作用域

list1 = [1, 9, 8, 4]
print( sorted(list1) )
print( sorted(list1, reverse=True) )
print( sorted(list1, True) )

reverse的传递方式使用关键字传递

def func(a, b, c, /, *, d, e, f):
    return( [a,b,c,d,e,f] )
print(func(1,2,3,d=4,e=5,f=6))

def solve(a, b, c):
    '''
    求解一元二次方程, 返回方程的两个根
    :para: a,b,c: int 方程系数
    :return: tuple
    '''
    delta = b*b - 4*a*c
    delta_sqrt = abs(delta)**0.5
    p1 = -b/2/a;
    p2 = delta_sqrt/2/a
    if delta>=0:
        root1 = p1 + p2
        root2 = p1 - p2
    else:
        root1 = complex(p1, p2)
        root2 = complex(p1, -p2)
    return root1, root2
print(solve.__doc__)
while True:
        try:
            a,b,c = eval(input('Enter eqution coefficient: '))
            if a == 0:
                raise
        except:
                print('invalid input, or, a is zero')
                break
        else:
            root1, root2 = solve(a, b, c)
            print(f'root1 = {root1:.2f}, root2 = {root2:.2f}')
            print()

def list_generator(b,e,s=1):
    l=[]
    while b<e:
        l.append(b+s)
        b=b+s
    return l
list1 = list_generator(-5, 5)
print(list1)
list2 = list_generator(-5, 5, 2)
print(list2)
list3 = list_generator(1, 5, 0.5)
print(list3)

def list_generator(begin, end, step=1):
    """生成特定范围区间"""
    ls = []
    a = begin
    b = end
    while a <= b:
        ls.append(a)
        a += step
    return ls


list1 = list_generator(-5, 5)
print(list1)
list2 = list_generator(-5, 5, 2)
print(list2)
list3 = list_generator(1, 5, 0.5)
print(list3)

def is_prime(n):
    if n==1:
        return False
    elif n==2:
        return True
    else:
        for i in range(2,n):
            if n%i==0:
                return False
                break
            else:
                return True
sushu=[]
for i in range(1,21):
    if is_prime(i)==True:
        sushu.append(i)
oushu=[]
for i in range(1,21):
    if i%2==0:
        oushu.append(i)
for n in oushu:
    for i in range(len(sushu)):
        for j in range(len(sushu)):
            if(n == sushu[i] + sushu[j]):
                print('{} = {} + {}'.format(n, sushu[i], sushu[j]))
                break
        if(n == sushu[i] + sushu[j]):
            break

 

def encoder(x):
    x = list(x)
    for i in range(len(x)):
        if('z' >= x[i].lower() >= 'v'):
            x[i] = chr(ord(x[i]) - 21)
        elif('v' > x[i].lower() >= 'a'):
            x[i] = chr(ord(x[i]) + 5)
    x = ''.join(x)
    return x
def decoder(x):
    x = list(x)
    for i in range(len(x)):
        if('a' <= x[i].lower() <= 'e'):
            x[i] = chr(ord(x[i]) + 21)
        elif('e' < x[i].lower() <= 'z'):
            x[i] = chr(ord(x[i]) - 5)
    x = ''.join(x)
    return x
wenben = input('输入英文文本；')
print('编码后的文本：{}'.format(encoder(wenben)))
print('对编码后的文本解码：{}'.format(decoder(encoder(wenben))))

def collatz(x):
    if(x % 2 == 0):
        x = int(x / 2)
    else:
        x = 3 * x + 1
    return x

list = []

try:
    n = eval(input('Enter a positive integer: '))

    if(n <= 0):
        raise
    elif(int(n) != n):
        raise

    while True:
        if(n == 1):
            list.append(n)
            break
        else:
            list.append(int(n))
            n = collatz(n)
    print(list)
except:
    print('Error: must be a positive integer')