py基础，常用sdk
一些要点
- python中是没有常量的关键字的，只是我们常常约定使用大写字符组合的变量名表示常量，也有“不要对其进行赋值”的提醒操作
PI = 3.14
- python3中有六个标准的数据类型： Number(数字)、String(字符串)、Boolean(布尔)、List(列表)、Tuple(元组)、Sets(集合)、Dictionary(字典)
不可变数据(4个)： Number(数字)、String(字符串)、Tuple(元组)、Boolean(布尔)
可变数据(3个)： List(列表)、Dictionary(字典)、Sets(集合)
python3支持三种不同的数值类型： 整型(int)、浮点型(float)、复数(complex)
字符串
lstrip、rstrip、strip、replace、find、ljust、rjust、isalpha、isdigit
text = ' abcdef125s wr2258abcd '
# 删掉开头和结尾的空格
print('original:', text)
print(' lstrip:', text.lstrip(' '))
print(' rstrip:', text.rstrip(' '))
print(' strip:', text.strip(' '))
print(' replace:', text.replace('a', 'A'))
print(' replace:', text.replace('a', 'A', 1))
print(' find:', text.find('a'))
# 填充字符***
print('text.ljust(50, \'*\') :', text.ljust(50, '*'))
print('text.rjust(50, \'*\') :', text.rjust(50, '*'))
print('text.center(50, \'*\') :', text.center(50, '*'))
# 判断是否全是字母/数字
print('isalpha:', 'abc -', 'abc'.isalpha(), '123 -', '123'.isalpha(), 'a12 -', 'a12'.isalpha())
print('isdigit:', 'abc -', 'abc'.isdigit(), '123 -', '123'.isdigit(), 'a12 -', 'a12'.isdigit())
输出：
original: abcdef125s wr2258abcd
lstrip: abcdef125s wr2258abcd
rstrip: abcdef125s wr2258abcd
strip: abcdef125s wr2258abcd
replace: Abcdef125s wr2258Abcd
replace: Abcdef125s wr2258abcd
find: 5
text.ljust(50, '*') : abcdef125s wr2258abcd *****************
text.rjust(50, '*') : ***************** abcdef125s wr2258abcd
text.center(50, '*') : ******** abcdef125s wr2258abcd *********
isalpha: abc - True 123 - False a12 - False
isdigit: abc - False 123 - True a12 - False
split和join
text2 = 'a,d,dw,d,s,w,t,c,w,'
list1 = text2.split(',')
print('text2:', text2)
print('list1:', list1)
print('join:', ','.join(list1))
输出
text2: a,d,dw,d,s,w,t,c,w,
list1: ['a', 'd', 'dw', 'd', 's', 'w', 't', 'c', 'w', '']
join: a,d,dw,d,s,w,t,c,w,
startswith和endswith
text3 = 'Hello world'
print('start with world:', text3.startswith('world'))
print('start with Hello:', text3.startswith('Hello'))
print('start with world:', text3.endswith('world'))
print('start with Hello:', text3.endswith('Hello'))
输出
start with world: False
start with Hello: True
start with world: True
start with Hello: False
空字符串表示否
空对象会输出None
text4 = ''
print(not text4) # 用于条件时，0、0.0、空字符串被认为是False
print(text4 == '')
sample
print(sample) # 对象为空会定义为None```
输出
True
True
None
list
list按index取值，: 用法，list * 2，list合并
list_1 = [1, 2, 3]
print('list_1 :'.rjust(11), list_1)
list_1.append(4)
print('append(4) :'.rjust(11), list_1)
print('[:1] :'.rjust(11), list_1[1:])
print('[:2] :'.rjust(11), list_1[:2])
print('[-1] :'.rjust(11), list_1[-1])
print('[:] :'.rjust(11), list_1[:])
print()
list_2 = [5, 6, 7]
list_merge = list_1 + list_2
print('list_2 :', list_2)
print('list_2 * 2 :', list_2 * 2)
print('list_1 + list_2 :', list_merge)
输出
list_1 : [1, 2, 3]
append(4) : [1, 2, 3, 4]
[:1] : [2, 3, 4]
[:2] : [1, 2]
[-1] : 4
[:] : [1, 2, 3, 4]
list_2 : [5, 6, 7]
list_2 * 2 : [5, 6, 7, 5, 6, 7]
list_1 + list_2 : [1, 2, 3, 4, 5, 6, 7]
list遍历，list按index取值，list插入，list移除，list随机排序，list排序，list判空
import random
my_list = [10, 20, 30]
print('my_list :', my_list)
print('my_list 遍历 :')
for item in my_list:
print(item)
a, b, c = my_list
print('a, b, c = my_list, a, b, c = ', a, b, c)
print('my_list.index(20) :', my_list.index(20))
my_list.insert(1, 15)
print('my_list.insert(1, 15) :', my_list)
my_list.remove(20)
print('my_list.remove(20) :', my_list)
random.shuffle(my_list)
print('random.shuffle(my_list) :', my_list)
my_list.sort()
print('my_list.sort() :', my_list)
my_list = []
print('my_list = [] :', my_list)
if not my_list:
print('if not my_list :', 'my_list is empty')
else:
print('if not my_list :', 'my_list is not empty')
输出
my_list : [10, 20, 30]
my_list 遍历 :
10
20
30
a, b, c = my_list, a, b, c = 10 20 30
my_list.index(20) : 1
my_list.insert(1, 15) : [10, 15, 20, 30]
my_list.remove(20) : [10, 15, 30]
random.shuffle(my_list) : [10, 30, 15]
my_list.sort() : [10, 15, 30]
my_list = [] : []
if not my_list : my_list is empty
list深拷贝
list_deep_copy = list_2[:]
list_2[1] = 2
print(list_2)
print(list_deep_copy)
输出
[5, 2, 7]
[5, 6, 7]
set
set创建，set遍历，set排序，set插入，discard尝试移除，pop操作，判断set存在，set清空
s0 = set()
s1 = set(list_1)
s2 = set({1, '2'})
print('s0 = set(), s0 :', s0)
print('s1 = set(list_1), s1 :', s1)
print('s2 = set({1, \'2\'}), s2 :', s2, '\n')
print('遍历 s2 :')
for item in s2:
print(item, type(item))
print('\n')
s2.add(3)
s2.add(4)
s2.add(5)
print('s2.add(3), s2.add(4), s2.add(5), s2 :', s2, '\n')
s2.discard(3)
print('s2.discard(3), s2 :', s2, '\n')
print('len(s2) :', len(s2), '\n')
print('s2.pop() :', s2.pop())
print('s2 :', s2, '\n')
if 4 in s2:
print('if 4 in s2 :', '4 in s2')
print('\n')
s2.clear()
print('s2.clear(), s2 :', s2, '\n')
输出
s0 = set(), s0 : set()
s1 = set(list_1), s1 : {1, 2, 3, 4}
s2 = set({1, '2'}), s2 : {1, '2'}
遍历 s2 :
1 <class 'int'>
2 <class 'str'>
s2.add(3), s2.add(4), s2.add(5), s2 : {1, '2', 3, 4, 5}
s2.discard(3), s2 : {1, '2', 4, 5}
len(s2) : 4
s2.pop() : 1
s2 : {'2', 4, 5}
if 4 in s2 : 4 in s2
s2.clear(), s2 : set()
tuple
tuple创建，tuple元素计数，tuple查找index
tuple1 = (1, 1, 3, 4, 5)
print(type(tuple1), '\n')
for item in tuple1:
print(item)
print('\n')
print(tuple1.count(1))
print(tuple1.index(5))
输出
<class 'tuple'>
1
1
3
4
5
2
4
dict
dict创建，dict取值，dict插入，嵌套dict，打印多层dict，dict设置默认值
my_dict = {'name': '张三', 'age': 18}
print(my_dict)
print(my_dict['name'])
my_dict['city'] = '北京'
print(my_dict)
print('\n')
print('name' in my_dict)
print('sex' in my_dict)
print('age' not in my_dict)
print('\n')
print(my_dict.setdefault('hobby', 'football'))
print(my_dict.setdefault('hobby', 'basketball'))
print('\n')
from pprint import pprint
dict = {'my_dict': my_dict, 'list_merge': list_merge, 's2': s2}
pprint(dict, indent=2)
print('\n')
输出
{'name': '张三', 'age': 18}
张三
{'name': '张三', 'age': 18, 'city': '北京'}
True
False
False
football
football
{ 'list_merge': [1, 2, 3, 4, 5, 6, 7],
'my_dict': {'age': 18, 'city': '北京', 'hobby': 'football', 'name': '张三'},
's2': set()}
if、while、for
if判断，while循环，for循环，双层for循环
name = '1'
if name == 'Alice':
print('Hi, I\'m Alice')
elif name == 'Bob':
print('Hi, I\'m Bob')
else:
print('Hi, I\'m', name)
print('\n')
cnt = 3
while cnt > 0:
print('cnt =', cnt)
cnt -= 1
print('\n')
for i in range(3):
print('i =', i)
print('\n')
tmp1 = [1,3,5,7,9]
tmp2 = [2,4,6,8,10]
tmp_list = [tmp1, tmp2]
print(tmp_list)
num_set = set(num for tmp in tmp_list for num in tmp)
print(num_set)
输出
Hi, I'm 1
cnt = 3
cnt = 2
cnt = 1
i = 0
i = 1
i = 2
[[1, 3, 5, 7, 9], [2, 4, 6, 8, 10]]
{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}
exception
def sample(divideBy):
try:
return 42/divideBy
except ZeroDivisionError:
print('error:invalid arguments')
print(sample(2)) # 输出21.0
print(sample(0)) # 打印错except信息，并输出None
输出
21.0
error:invalid arguments
None
参考：
https://zhuanlan.zhihu.com/p/694203031
https://blog.csdn.net/m0_56051805/article/details/126900242
