写在前面
本系列教程针对有一定编程经验的伙伴快速入门python基础,一些涉及开发的常识问题,本文并不涉及。
if else
is_hot= False
is_cold= True
if is_hot : (可以使用 and or 连接多个条件 not 可取反)
print("It's a hot day")
elif is_cold:
print("It's a cold day")
else:
print("It's a cold day")
print("Enjoy your day")
=>
It's a cold day
Enjoy your day
while
i=1
while i<=5:
print(i)
i +=1
else:
print(2) 跳出后执行一次
=> 1 2 3 4 5 2
for
for item in 'python': print(item)
=>
p
y
t
h
o
n
for item in ['Mosh','John','Sarah']:
print(item)
=>
Mosh
John
Sarah
for item in range(10):
print(item)
=> 0 1 2 3 4 5 6 7 8 9
for item in range(5,10):
print(item) =>5~9
for item in range(5,10,2): 步长
print(item) => 5,7,9
循环嵌套
for x in range(4):
for y in range(3):
print(f'({x},{y})')
=>
(0,0)
(0,1)
(0,2)
(1,0)
(1,1)
(1,2)
(2,0)
(2,1)
(2,2)
(3,0)
(3,1)
(3,2)
数组
matrix=[ [1,2,3], [4,5,6], [7,8,9] ] print(matrix[0]) print(matrix[1][1]) print(matrix[2][2]) => [1, 2, 3] 5 9
for row in matrix:
for num in row:
print(num)
=>
1
2
3
4
5
6
7
8
9
添加
numbers=[1,2,3,4,5,6]
numbers.append(10)
print(numbers)
=>
[1, 2, 3, 4, 5, 6, 10]
插入
numbers=[1,2,3,4,5,6]
numbers.insert(1,10)
print(numbers)
=>[1, 10, 2, 3, 4, 5, 6]
删除
numbers=[1,2,3,4,5,6]
numbers.remove(1)
print(numbers)
=>
[2, 3, 4, 5, 6]
numbers=[1,2,3,4,5,6]
numbers.remove(0)
print(numbers)
=>
报错
ValueError: list.remove(x): x not in list
清空
numbers=[1,2,3,4,5,6]
numbers.clear()
print(numbers)
=>[]
末尾删除,出栈
numbers=[1,2,3,4,5,6]
numbers.pop()
print(numbers)
=>[1, 2, 3, 4, 5]
查找
numbers=[1,2,3,4,5,6]
print(numbers.index(5))
=>4
计算个数
numbers=[1,2,3,4,5,6]
print(numbers.count(5))
=>1
排序
numbers=[1,4,3,2,5,6]
numbers.sort()
print(numbers)
=>[1, 2, 3, 4, 5, 6]
反转
numbers=[1,4,3,2,5,6]
numbers.reverse()
print(numbers)
=>[6, 5, 2, 3, 4, 1]
不改变原有数组复制
numbers=[1,4,3,2,5,6]
numbers2=numbers.copy()
numbers.remove(3)
print(numbers2)
=>
[1,4,3,2,5,6]
会改变原有对象
numbers=[1,4,3,2,5,6]
numbers2=numbers
numbers.remove(3)
print(numbers2)
=>[1, 4, 2, 5, 6]
不能被修改的元组
numbers=(1,2,3) numbers[0]=23 print(numbers) => 报错 TypeError: 'tuple' object does not support item assignment
压缩特性
coordinates=(1,2,3) x=coordinates[0] y=coordinates[1] z=coordinates[2] '''等同于''' x,y,z=coordinates
键值对
customer={ "name":"Jay chou", "age":30 } print(customer["birthday"])=>报错
print(customer.get("birthday"))=>None
customer["birthday"]="1993/12/22" 添加新键值对
print(customer.get("birthday"))
=>
1993/12/22
print(customer.get("xxx","!"))
=>!