实验四

task1

print(sum)
sum = 42
print(sum)
def inc(n):
    sum = n+1
    print(sum)
    return sum
sum = inc(7) + inc(7)
print(sum)

task2

1.内置函数

2.给sum赋予一个值

3.局部变量

4.全局变量

def func1(a, b, c, d, e, f):
    '''
    返回参数a,b,c,d,e,f构成的列表
    默认，参数按位置传递; 也支持关键字传递
    '''
    return [a,b,c,d,e,f]

def func2(a, b, c,*, d, e, f):
    '''
    返回参数a,b,c,d,e,f构成的列表
    *后面的参数只能按关键字传递'''
    return [a,b,c,d,e,f]

def func3(a, b, c, /, d, e, f):
     '''
    返回参数a,b,c,d,e,f构成的列表
    /前面的参数只能按位置传递'''
     return [a,b,c,d,e,f]

    #func1调用：按位置传递、按参数传递都可以
print( func1(1,9,2,0,5,3) )
print( func1(a=1, b=9, c=2, d=0, e=5, f=3) )
print( func1(1,9,2, f=3, d=0, e=5))


# func2调用：d,e,f必须按关键字传递
print( func2(11, 99, 22, d=0, e=55, f=33) )
print( func2(a=11, b=99, c=22, d=0, e=55, f=33) )


# func3调用：a,b,c必须按位置传递
print( func3(111, 999, 222, 0, 555, 333))
print( func3(111, 999, 222, d=0, e=555, f=333))

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

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

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



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()

 

task4

def list_generator(x,y,s=1):
    l=[]
    while x<=y :
        l.append(x)
        x=x+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)

task5

def is_prime(n):
    if n == 2:
        return True
    else:
        for i in range (2,int(n**0.5)+1):
            if n%i == 0:
                return False
        return True
for i in range(4,21,2):
    for s in range(2,i):
        if is_prime(i-s):
           print(f"{i} = {s} + {i-s}")
           break

task6

def encoder(a):
    b = 5
    c = ''
    for i in a:
        if i.isalpha():
            temp = ord(i)+b
            if chr(temp).isalpha():
                c += chr(temp)
            else:
                c += chr(temp-26)
        else:
            c += i
    return c

def decoder(x):
    y = 5
    z = ''
    for i in x:
        if i.isalpha():
            temp = ord(i)-y
            if chr(temp).isalpha():
                z += chr(temp)
            else:
                z += chr(temp+26)
        else:
            z += i
    return z

text=input('输入英文文本:')
print('加密后的文本是：',encoder(text))
print('解码后的文本是：',decoder(encoder(text)))

task7

def collatz(a):
    l=[a]
    while l[-1] != 1:
        if l[-1] % 2 == 0 :
            l.append((l[-1])//2)
        else:
            l.append((l[-1])*3+1)
    return l

try:
    x=int(input('enter a positive integer'))
    if x <= 0:
        raise
except:
    print('Error: must be a positive integer')
else:
    print(collatz(x))