一步一步学Python(1) 基本逻辑控制举例和编码风格规范

>>> import time
>>> i = 0
>>> while 1:
...     i += 1
...     print(i)
...     time.sleep(3)
... 
1
2
3
^CTraceback (most recent call last):
  File "<stdin>", line 4, in <module>
KeyboardInterrupt
>>> 

>>> for i in range(3):
...     print("old i = " + str(i))
...     i += 1
...     print("new i = " + str(i))
... 
old i = 0
new i = 1
old i = 1
new i = 2
old i = 2
new i = 3
>>> 

$ more if.py

x = int(input("Please enter an integer: "))
if x < 0:
    x = 0
    print(‘Negative changed to zero‘)
elif x == 0:
    print(‘Zero‘)
elif x == 1:
    print(‘Single‘)
else:
    print(‘More‘)

$ python3 if.py 
Please enter an integer: -1
Negative changed to zero
$ python3 if.py 
Please enter an integer: 0
Zero
$ python3 if.py 
Please enter an integer: 1
Single
$ python3 if.py 
Please enter an integer: 2
More