Python基础知识11（# python中常用小技巧总结 ）
# 1 字典的合并 merge
dict_a = {
"a": 13,
"b": 14,
"c": 15
}
dict_b = {
"d": 19,
"b": 200,
"e": 16
}
dict_c = {**dict_a, **dict_b} #merge
# dict_d = dict_a | dict_b
print(dict_c)
# print(dict_d)
#2 slice()切片
s = slice(3,6)
s2 = slice(3,None) #到最后。
list1 = [1,3,'a',5,11,16,19,20,11]
list2 = [1,3,'a',5,2,12,13,21,31]
print(list1[s])
print(list2[s])
#3
import heapq
取list中的值
s = [51,33,64,87,99,75,15,49,33,82]
print(heapq.nlargest(5, s))#[99, 87, 82, 75, 64]，输出s中5个最大的值，并逆序pail
print(heapq.nsmallest(3, s))#[15, 33, 33] ，输出s中3个最小的值，并正序排列
#4占位符和正则写法
_, *s, _ = [1,2,3,4,5,6,7,8]
print(s)#[2, 3, 4, 5, 6, 7]
#5
x = 3
print( 1 < x and x < 10)
print( 1< x <10) #类似于数学上的写法
#6 把字符串 变成真正的列表
string = "[[1,2,3], [4,5,6]]"
import ast
def string_to_list(string):
return ast.literal_eval(string)
list3 = string_to_list(string)
print(list3)
#7 print()#sep="@"合并打印
print("abc","163.com", sep="@")#abc@163.com
#8 数字
n = 123
# n1 = 0111 #不能以0开头
print(1_000_000_000)
#9 == 和is的区别
list4 = [1,2,3]
list5 = [1,2,3]
print(list4 == list5) 元素值相等
print(list4 is list5) # => id()不同
#10 判断是不是以传入的字符串为开头
str1 = "abcdefg"
print(str1.startswith('b'))
#11 set的add添加元素
set1 = {1,2,3,5}
set1.add('a')
print(set1)
set2 = frozenset(['a','b','c'])
# set2.add('d') #'frozenset' object has no attribute 'add'
print(set2)
#12 uicode 字符编号
print(ord('A'))#65
print(ord('B'))#66
print(ord('C'))#67
#13 字典 key 和 value 的互换
dict1 = {1: 'a', 2: 'b', 3: 'c' }
dict2 = {j:i for i, j in dict1.items() } #推导式
print(dict2)
#14 bool
# 所有的值都有布尔值
print(bool('d'))
print(bool(''))
print(bool(0))
print(bool(1))
#15 复数
c = complex(10,2)
print(c)
h = hex(11)
print(h)
#16 lamda 函数 只能写在一行 one line 如果有 if 后面一定要有else
l = lambda x: "x > 3" if x > 3 else "x <=3"
print(l(2))
#17 字符串 判断空格
string1 = "a"
r = string1.isspace()
print(r)
# 判断字符串是不是数字
string2 = "123a"
r2 = string2.isdigit()
print(r2)
#判断中文的数字 还能识别大写的汉字
string3 = "四五六陆"
r3 = string3.isnumeric()
print(r3)
#判断一个字符串 的每个单子首字母是不是大写
string4 = "I Am Human"
r4 = string4.istitle()
print(r4)
#18 print()
def is_positive(n:int):
print("大于0" if n > 0 else "小于等于0")
is_positive(-1)
#19 if all 和any
m_p = 51
b_p = 78
p_p = 100
conditions = [m_p > 60, b_p> 60 ,p_p>60 ]
if all(conditions):
print("全部科目及格了")
else:
print("有的科目挂了")