py基礎，常用sdk
一些要點
- python中是沒有常量的關鍵字的，只是我們常常約定使用大寫字符組合的變量名表示常量，也有“不要對其進行賦值”的提醒操作
PI = 3.14
- python3中有六個標準的數據類型： Number(數字)、String(字符串)、Boolean(布爾)、List(列表)、Tuple(元組)、Sets(集合)、Dictionary(字典)
不可變數據(4個)： Number(數字)、String(字符串)、Tuple(元組)、Boolean(布爾)
可變數據(3個)： List(列表)、Dictionary(字典)、Sets(集合)
python3支持三種不同的數值類型： 整型(int)、浮點型(float)、復數(complex)
字符串
lstrip、rstrip、strip、replace、find、ljust、rjust、isalpha、isdigit
text = ' abcdef125s wr2258abcd '
# 刪掉開頭和結尾的空格
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, '*'))
# 判斷是否全是字母/數字
print('isalpha:', 'abc -', 'abc'.isalpha(), '123 -', '123'.isalpha(), 'a12 -', 'a12'.isalpha())
print('isdigit:', 'abc -', 'abc'.isdigit(), '123 -', '123'.isdigit(), 'a12 -', 'a12'.isdigit())
輸出：
original: abcdef125s wr2258abcd lstrip: abcdef125s wr2258abcd rstrip: abcdef125s wr2258abcdstrip: abcdef125s wr2258abcdreplace: 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))
輸出
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'))
輸出
start with world: False
start with Hello: True
start with world: True
start with Hello: False
空字符串表示否
空對象會輸出None
text4 = ''
print(not text4) # 用于條件時，0、0.0、空字符串被認為是False
print(text4 == '')sample
print(sample) # 對象為空會定義為None```
輸出
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)
輸出
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遍歷，list按index取值，list插入，list移除，list隨機排序，list排序，list判空
import randommy_list = [10, 20, 30]
print('my_list :', my_list)print('my_list 遍歷 :')
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')
輸出
my_list : [10, 20, 30]
my_list 遍歷 :
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深拷貝
list_deep_copy = list_2[:]
list_2[1] = 2
print(list_2)
print(list_deep_copy)
輸出
[5, 2, 7]
[5, 6, 7]
set
set創建，set遍歷，set排序，set插入，discard嘗試移除，pop操作，判斷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('遍歷 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')
輸出
s0 = set(), s0 : set()
s1 = set(list_1), s1 : {1, 2, 3, 4}
s2 = set({1, '2'}), s2 : {1, '2'} 遍歷 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 s2s2.clear(), s2 : set()
tuple
tuple創建，tuple元素計數，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))
輸出
<class 'tuple'> 1
1
3
4
52
4
dict
dict創建，dict取值，dict插入，嵌套dict，打印多層dict，dict設置默認值
my_dict = {'name': '張三', '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 pprintdict = {'my_dict': my_dict, 'list_merge': list_merge, 's2': s2}
pprint(dict, indent=2)
print('\n')輸出
{'name': '張三', 'age': 18}
張三
{'name': '張三', 'age': 18, 'city': '北京'}True
False
Falsefootball
football{ 'list_merge': [1, 2, 3, 4, 5, 6, 7],'my_dict': {'age': 18, 'city': '北京', 'hobby': 'football', 'name': '張三'},'s2': set()}
if、while、for
if判斷，while循環，for循環，雙層for循環
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)輸出
Hi, I'm 1cnt = 3
cnt = 2
cnt = 1i = 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/divideByexcept ZeroDivisionError:print('error:invalid arguments')print(sample(2)) # 輸出21.0
print(sample(0)) # 打印錯except信息，并輸出None
輸出
21.0
error:invalid arguments
None
參考：
https://zhuanlan.zhihu.com/p/694203031
https://blog.csdn.net/m0_56051805/article/details/126900242
