根据《Python编程入门经典》（James Payne著，张春晖译）整理。

 

比较两个值是否相等。

>>> 1 == 1
True
>>> 1 == -1
False
>>> a = ["a", "b", "c"]
>>> b = ["a", "b", "cd"]
>>> a == b
False

比较两个值是否不相等。

>>> 1 !=1
False
>>> 1 != 2
True

比较两个值大小。

>>> 3 > 2
True

取反。

>>> not True
False
>>> not False
True

和运算。

>>> 1 == 1 and 2 == 2
True
>>> 1 !=1 and 2 == 2
False

或运算。

>>> 1!=1 or 2 == 2
True
>>> 1 != 1 or 2 != 2
False

 

if

>>> if 2 > 1:
...   print("yes")
...
yes

嵌套

>>> omelet_ingredients = {"egg":2, "mushroom":5, "pepper":1, "cheese":1, "milk":1}
>>> fridge_contents = {"egg":10, "mushroom":20, "pepper":3, "cheese":3, "tomato":4, "milk":15}
>>> if(omelet_ingredients["egg"] < fridge_contents["egg"]):
...   have_ingredients[0] = True
...   have_ingredients.append("egg")
...
>>> print(have_ingredients)
[True, 'egg']
>>> if(omelet_ingredients["mushroom"] < fridge_contents["mushroom"]):
...   if(have_ingredients[0] == False):
...     have_ingredients[0] = True
...   have_ingredients.append("mushroom")
...
>>> print(have_ingredients)
[True, 'egg', 'mushroom']

 

循环

while

>>> i = 10
>>> while i > 0:
...   print(i)
...   i = i-1
...
10
9
8
7
6
5
4
3
2
1

for

>>> for i in range(5):
...   print(i)
...
0
1
2
3
4

>>> for i in range(10, 0, -2):
...   print(i)
...
10
8
6
4
2

break

终止循环。

>>> for i in range(10, 0, -1):
...   print(i)
...   if i == 5:
...     break
...
10
9
8
7
6
5

continue

跳过当前循环。

>>> i = 10
>>> while i > 0:
...   i = i - 1
...   if i == 3:
...     continue
...   print(i)
...
9
8
7
6
5
4
2
1
0