python基础知识漏洞总结

Posted 2020-12-05 listash

1.字符串格式化: format

1 # format
2 s0 = "我叫{},今年{}岁了,我喜欢{}".format("王力宏",46,"娃哈哈")    #按位置格式化
3 s1 = "我叫{0},今年{2}岁了,我喜欢{1}".format("王力宏","娃哈哈",46)    #指定位置格式化
4 s2 = "我叫{name},今年{age}岁了,我喜欢{lover}".format(name = "王力宏",age = 46,lover = "徐静蕾") #指定关键字
5 print(s0)
6 print(s1)
7 print(s2)

2.迭代添加:extend

1 li = ["a","b","c"]
2 li.extend("xyz")
3 print(li)

3.去重复

　　1)利用set特性

1 l1 = [‘c‘, ‘d‘, ‘r‘, ‘d‘, ‘r‘ ,‘a‘, ‘C‘]
2 l2 = list(set(l1))
3 l2.sort(key=l1.index)   #set内元素是无序的,用sort可以按照L1的元素顺序排序
4 print(l2)

　　2)for循环

1 l1 = [‘c‘, ‘d‘, ‘r‘, ‘d‘, ‘r‘ ,‘a‘, ‘C‘]
2 l2 = []
3 for el in l1:
4     if el not in l2:
5         l2.append(el)
6 print(l2)

　　3)排序后while循环

 1 l1 = [‘c‘, ‘d‘, ‘r‘, ‘d‘, ‘r‘ ,‘a‘, ‘C‘]
 2 l1.sort()
 3 l2=[]
 4 n = 0
 5 while n < len(l1):
 6     if l1[n] not in l2:
 7         l2.append(l1[n])
 8         n = n + 1
 9     else:
10         n = n + 1
11 print(l2)

 

4.小数据池

 

5.深浅copy

1)浅拷贝: 只拷贝第一层,下层沿用(地址相同)

1 l1 = ["蚂蚁","蓝猫","影魔"]
2 l2 = l1.copy()
3 l1.append("帕克")
4 print(l1)
5 print(l2)
6 print(id(l1),id(l2))
7 # [‘蚂蚁‘, ‘蓝猫‘, ‘影魔‘, ‘帕克‘]
8 # [‘蚂蚁‘, ‘蓝猫‘, ‘影魔‘]
9 # 2527144744328 2527144744264

l1 = ["蚂蚁","蓝猫","影魔",["巨魔","飞机","莉娜"]]
l2 = l1.copy()
l1[3].append("帕克")
print(l1)
print(l2)
print(id(l1[3]),id(l2[3]))
# [‘蚂蚁‘, ‘蓝猫‘, ‘影魔‘, [‘巨魔‘, ‘飞机‘, ‘莉娜‘, ‘帕克‘]]
# [‘蚂蚁‘, ‘蓝猫‘, ‘影魔‘, [‘巨魔‘, ‘飞机‘, ‘莉娜‘, ‘帕克‘]]
# 2988850058632 2988850058632

2)深拷贝: 完全不同的个体

import copy
l1 = ["蚂蚁","蓝猫","影魔",["巨魔","飞机","莉娜"]]
l2 = copy.deepcopy(l1)  #注意用法,需要导入copy模块
l1[3].append("帕克")
print(l1)
print(l2)
print(id(l1[3]),id(l2[3]))
# [‘蚂蚁‘, ‘蓝猫‘, ‘影魔‘, [‘巨魔‘, ‘飞机‘, ‘莉娜‘, ‘帕克‘]]
# [‘蚂蚁‘, ‘蓝猫‘, ‘影魔‘, [‘巨魔‘, ‘飞机‘, ‘莉娜‘]]
# 1751479821960 1751479823368

 

6.fromkeys

1 dic = dict.fromkeys(["jay","JJ"],["周杰伦","林俊杰"])
2 print(dic)
3 # {‘jay‘: [‘周杰伦‘, ‘林俊杰‘], ‘JJ‘: [‘周杰伦‘, ‘林俊杰‘]}
4 dic.get("jay").append("哈哈哈")
5 print(dic)
6 # {‘jay‘: [‘周杰伦‘, ‘林俊杰‘, ‘哈哈哈‘], ‘JJ‘: [‘周杰伦‘, ‘林俊杰‘, ‘哈哈哈‘]}  由于dic中jay和JJ共用一个列表,jay添加元素,相应JJ也添加元素

7.文件操作的r+模式

r+模式是追加读写,但并不是只能先读后写,也可以先写后读,注意先读后写时,只能再末尾添加

8.空元组的表示方法

(,) 注意中间要有逗号

9.join用法

split()可以分割字符串成列表,而join()可以将列表中的元素拼接成字符串

10.解码编码

 

11.setdefault用法