循環語句

馮羅伊曼體系架構

1.?輸入設備

2.?輸出設備

3.?存儲器

4.?運算器

5.?控制器

轉義序列：\\, \t , \r , \n , \”, ?\’

Python:是動態語言，強類型語言

算數運算符

+ – */ % **

/是自然除，//是整除

位運算符

& | ?~ ?^ ?<< ?>>

原碼 5=> 0b101, 1=>0b1, -1=>-0b1, bin(-1)

反碼：正數的反碼與原碼相同；負數的反碼符號位不變其余按位取反

補碼：正數的補碼與原碼相同；負數的補碼符號位不變其余位取反后加一

比較運算符：== ！= > < >= <=

邏輯運算符

與或非 and ?or ?not

短路運算符

and如果第一個表達式為false，后面沒必要計算，邏輯表達式一定是false

or如果第一個表達式為true，后面沒必要計算，邏輯表達式一定是true

內存管理：GC就是回收站

If elif else語句

?例子

a=100

if a<0:

????print(‘negative’)

elif a==0:

????print(‘zero’)

else:

????print(‘positive’)

嵌套

scroe=80

if scroe<80:

????print(‘wrong’)

????else:

????????if scroe==0:

???????? print(‘egg’)

????????elif scroe<=100:

????????????print(‘right’)

????????else:

????????????print(‘too big’)

練習

輸入兩個數字，輸出最大數

a=input(‘input a number a:’)

b=input(‘input a number b:’)

if a>b:

????print(a)

elif b>a:

????print(b)

else:

????print(a)

給定一個不超過五位的正正整數，判斷其有幾位

a= 100

if a<10:

????print(‘1’)

elif a<100:

????print(‘2’)

elif a<1000:

????print(‘3’)

elif a<10000:

????print(‘4’)

else:

????print(‘try agin’)

例子2

val = input(‘>>>’)

val = int(val)

if val >= 1000: #fold

????????if val>= 10000:

????????????print(5)

????????else:

????????????print(4)

else:

????????if val >= 100:

????????????print(3)

????????elif val >= 10:

????????????print(2)

????????else:

????????????print(1)

While循環

例子

flag = 10

while flag:

????print(flag)

????Flag -= 1

for循環

例子

for i in range(10):

????print(i+1)

例子10以內的偶數

for i in range(10):

????if not i%2:

????????print(i)

課堂案例：

1.輸入一個數，判斷幾位，并把它從最高位打到最低位（5位以內）

val = input(‘>>>’)

val = int(val)

if val >= 1000:

????if val >= 10000:

????????num = 5

????else:

????????num = 4

else:

????if val >= 100:

????????num = 3

????elif var >= 10:

????????num = 2

????else:

????????num = 1

print(num)

c = val

for i in range(num):

????n = c//10

print(c – n*10)

c = n

2.打印一個正方形

n = 5

print(‘*’*n)

for i in range(n-2):

????print(‘*’+’ ‘*(n-2)+’*’)

print(‘*’*n)

3.?求100以內的奇數和

y = 0

for i in range(1,100,2):

????y = (i + y)

print(y)

4.?判斷學生成績

i=input(‘>>>’)

i=int(i)

if 100>=i>=90:

????print(‘A’)

elif 90>i>=80:

????print(‘B’)

elif 80>i>=70:

????print(‘C’)

elif 70>i>=60:

????print(‘D’)

else :

print(‘E’)

5.1-5的階層之和

a=1

for i in range(1,6,1):

????a = a*i

print(a)

6#判斷是否為質數

yum = input(‘>>>’)

yum = int(yum)

for i in range(2,yum):

????if not yum % i:

????????print(‘no’)

????????break

else:

???print(‘yes’)

7#打印99乘法表

for i in range(1,10):

????for o in range(1,i+1):

????????print(‘{}*{}={}\t’.format(i,o,i*o),end=”)

print()

8#打印菱形

a=input(‘請輸入奇數‘)

a=int(a)

for i in range(-a,a+1):

????if i < 0:

????????i=-i

print(” “*i+’*’*(a-2*i)+” “*i)

#打印100以內的斐波那契數列

a=0

b=1

while b<100:

????print(b)

a,b=b,a+b

#打印101項斐波那契數列

a=0

b=1

for i in range(1,101):

????a,b=b,a+b

print(b)

#打印100000以內的質數

for a in range(2,100000):

????for i in range(2,a):

????????if not a%i :

????????????break

????else:

????????print(a)

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