实验四

#task1.py
print(sum)
sum=42
print(sum)

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

sum=inc(7)+inc(7)
print(sum)

 

 

答：不是。

line1：内置

line3，line11：全局

line7：局部

#task2_2.py
list1=[1,9,8,4]

print(sorted(list1))
print(sorted(list1,reverse=True))
print(sorted(list1,True))

 

 python内置函数sorted（）中，参数reverse的传递方式必须使用关键字传递

#task2_3.py
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))

 

 

#task3.py
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()

 

 无法打印出来。

#task4.py
def list_generator(begin,end,step=1):
    x = []
    i = begin
    while i >= begin and i<= end:
        x.append(i)
        i += step
    return x

list1=list_generator(-5, 5)
print(list1)

list2=list_generator(-5, 5, 2)
print(list2)

list3=list_generator(1, 5, 0.5)
print(list3)

 

 

#task5.py
def is_prime(n):
    if n < 2:
        return False
    for i in range(2,int(n**0.5)+1):
        if n % i == 0:
            return False
    return True


y=[i for i in range(21)]
for x in y[::2]:
    for a in range(0,20):
        if is_prime(a) == True:
            if is_prime(x-a)==True:
                print(f'{x}={a}+{x-a}')
                break
            else:
                a+=1
        else:
            a+=1

 

 

#task6.py
def encoder(z):
    a = list(z)
    i = 0
    while i < len(z):
        x = ord(a[i])
        if 65 <= x <= 85 or 97 <= x <= 117:
            y = chr(x + 5)
        elif 85 < x <= 90 or 117 < x <= 122:
            y = chr(x - 21)
        else:
            y = chr(x)
        a[i]=y
        i += 1
    return ''.join(a)


def decoder(z):
    a = list(z)
    i = 0
    while i < len(z):
        x = ord(a[i])
        if 70 <= x <= 90 or 102 <= x <= 122:
            y = chr(x - 5)
        elif 65 <= x < 70 or 97 <= x < 102:
            y = chr(x + 21)
        else:
            y = chr(x)
        a[i]=y
        i += 1
    return ''.join(a)


z = input('输入英文文本:')
print(f'''编码后的文本：{encoder(z)}
对编码后的文本解码：{decoder(encoder(z))}''')

 

 

#task7.py
def Collatz(n):
    if n % 2 == 0 and n > 0:
        return int(n / 2)
    if n % 2 != 0 and n > 0:
        return int(3 * n + 1)


x = []
a = int(input('Enter a positive integer: '))
while True:
    try:
        if a != 1:
            x.append(a)
            a = Collatz(a)
        else:
            x.append(a)
            break
    except:
        print('Error : must be a positive integer')
        break
print(x)