python

交互模式下面默認調用repr(a)這個方法

>>>a=1
>>>a
1

代碼塊，多敲一次回車

>>> n=10
>>> if n==10:
...     
...     print ("equal")
... else:
...     
...     print ("not equal")
... 
equal
>>> print ("a")  
a

input 讀入的都是字符串

>>> s=input("請輸入一個數字：")
請輸入一個數字：10
>>> s
'10'
>>> print ("s")
s
>>> print (s)  
10
>>> 
>>> type(s) 
<class 'str'>

>>> myage=input("請輸入的生日的月份：")  
請輸入的生日的月份：6
>>> if myage==7
  File "<stdin>", line 1
    if myage==7
              ^
SyntaxError: invalid syntax
>>>     
>>> if myage==7:
...     
...     print ("its my age")
... else:
...     
...     print ("its not my age")
... 
its not my age
>>> 

列表、元組和字符串都是序列

>>> for i in range(5):
...     
...     print (i)
... 
0
1
2
3
4
>>> for i in "abc"
  File "<stdin>", line 1
    for i in "abc"
                 ^
SyntaxError: invalid syntax
>>> for i in "abc":
...     
...     print (i)
... 
a
b
c
>>> for i in int[1,2,3]:
...     
...     print (i)
... 
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'type' object is not subscriptable
>>> for i in [1,2,3]:   
...     
...     print (i)
... 
1
2
3
>>> for i in (1,2,3):
...     
...     print (i)
... 
1
2
3

>>> for i in range(5,10):
...     
...     print (i)
... 
5
6
7
8
9

>>> for i in range(10,-1,-1):
...     
...     print (i)
... 
10
9
8
7
6
5
4
3
2
1
0

for i in range(10,-1,-1):
…
… continue
…
… print (i)
…

for i in range(10,-1,-1):
…
… if (i==5):
…
…
… print(i)
…
5

for i in range(10,-1,-1):
…
… if(i==5):
…
…
… break
…

>>> for i in range(10):
...     if i==8:
...         break
... else:
...     print("no break")
...
>>> for i in range(10):
...     continue
... else:
...     print("no break!")
...
no break!

>>> for i in range(10,-1,-1):
...     if(i==8):            
...     
...             
...             break
... else:
...     
...     print ("no break")
... 
>>> for i in range(10,1,1):
...     
...     continue
... else:
...     
...     print("no break")
... 
no break
>>> 

>>> for i in range(10):
...     
...     if i%2==1:
...     
...             
...             continue
...     
...     print(i)
... 
0
2
4
6
8
>>> 
>>> for i in range(10):
...     
...     if(i%2==1):
...     
...             
...             break
...     
...     print (i)
... 
0
>>> 

where

>>> while n>=1:
...     
...     print (n)
...     
...     n-=1
... 
5
4
3
2
1
>>> n=n-1  -->n-=1

>>> while n>=1:
...     
...     if n>=2:
...     
...             
...             print (n)
...     
...     else:
...     
...             
...             break    
...     
...     n-=1
... 
5
4
3
2
>>> 
>>> while 1:
...     
...     break
... else:
...     
...     print ("no")
... 
>>> n=5
>>> while n>=6:
...     
...     print (n)
... else:
...     
...     print("no break")
... 
no break
>>> 

練習2：
你可以輸入3種字母：e、a、r
如果等於e，那麼退出循環

如果輸入 a,執行continue

如果輸入r,那麼再讀取一次字母，並打印

只允許輸入三次字母，重輸入字母的不算在內

while 1:
    letter = input("請輸入指令")
    if letter == "e":
        break
    elif letter =="a":
        continue
    elif letter == "r":
        letter = input("請輸入指令")
        print(letter)

n=3
while n>=1:
    letter = input("請輸入指令")
    n-=1
    if letter == "e":
        break
    elif letter =="a":
        continue
    elif letter == "r":
        letter = input("請輸入指令")
        print(letter)