python 列表，元组

print()函数查看帮助文件

>>> help(print) Help on built-in function print in module builtins: print(...) print(value, ..., sep=' ', end='\n', file=sys.stdout, flush=False) Prints the values to a stream, or to sys.stdout by default. Optional keyword arguments: file: a file-like object (stream); defaults to the current sys.stdout. sep: string inserted between values, default a space. end: string appended after the last value, default a newline. flush: whether to forcibly flush the stream.

语法格式：

print(value, ..., sep=' ', end='\n', file=sys.stdout, flush=False) >>> a=1 >>> b=2 >>> d=[1,2,3] >>> print(a,b,d) 1 2 [1, 2, 3] >>> print(a,b,d,sep="$") 1$2$[1, 2, 3]

格式化字符串

%号格式化

name = "Tom" age = 18 print("His name is %s, his age is %d." % (name, age)) print("His name is " + name + ", his age is " + str(age) +".")

His name is Tom, his age is 18. His name is Tom, his age is 18.

>>> a=100 >>> "%d%%"%a '100%'

格式：print(" % " %变量名)

占位符

格式描述%d有符号的整数ASCII码%s字符串%c字符及ASCII码%o无符号八进制%x/%X无符号十六进制%e/%E科学计数法%f浮点数

format格式化

name = "Tom" age = 18 print("His name is %s, his age is %d." %(name, age)) print("His name is {}, his age is {}.".format('Tom',18))

Guangzhou,Name: Tom, age: 18 第一个元素是：baidu

[基本语法是通过{}和：来替代以前的%]

格式：print(" …{} ".format(‘tom’/18))

列表

列表使用方括号[],每个元素逗号分隔；

可以储存不同的数据类型数据

数组

特点：有序，可重复，可变类型

创建

#- 创建空列表 li = [] print(type(li)) # - 创建多元素列表 li = [1, 2, 3, "abcd", "City", "College", ["I","love", "python"]] print((li,type(li))) # - 强转 sr = "abcd " li = list(sr) print((li,type(li)))

<class ‘list’> ([1, 2, 3, ‘abcd’, ‘City’, ‘College’, [‘I’, ‘love’, ‘python’]], <class ‘list’>) ([‘a’, ‘b’, ‘c’, ‘d’, ’ '], <class ‘list’>)

#(1)拼接 li1 = ["I"] li2 = ["love","python"] print(li1+li2) #(2)重复 print(li2*3) #(3)索引（偏移）[],切片[:],[::] li = ["C","i","t","y","City","College","Zhejiang",["City","College","Zhejiang"]] print(len(li)) print((li[0],li[-7])) print(li[:5]) print(li[::-1]) print(li[7][1])

[‘I’, ‘love’, ‘python’] [‘love’, ‘python’, ‘love’, ‘python’, ‘love’, ‘python’] 8 (‘C’, ‘i’) [‘C’, ‘i’, ‘t’, ‘y’, ‘City’] [[‘City’, ‘College’, ‘Zhejiang’], ‘Zhejiang’, ‘College’, ‘City’, ‘y’, ‘t’, ‘i’, ‘C’] College

列表的常见操作

增 li = ["City","College"] print(id(li)) li1 = ["a","b","c"] li.append(li1) print((li,id(li))) li = ["a","b"] print(id(li))

1295698911880 ([‘City’, ‘College’, [‘a’, ‘b’, ‘c’]], 1295698911880) 1295700185160

#extend() li = ["City","College"] #print(id(li)) li1 = ["a","b","c"] li.extend(li1) print(li) #insert(),按照索引添加 li.insert(1,li1) print(li)

[‘City’, ‘College’, ‘a’, ‘b’, ‘c’] [‘City’, [‘a’, ‘b’, ‘c’], ‘College’, ‘a’, ‘b’, ‘c’]

#改 li = ['City', ['a', 'b', 'c'], 'College', 'a', 'b', 'c'] li[5] = "6666" li[2:6] = ["x","y","z"] print(li[2:6]) #删 # - pop(),返回被删除的元素 # - 若不指定索引，默认删除最后一个元素 # - 删除指定索引对应的元素 li = ["a","b","c","d","e"] print(li.pop(2)) print(li) # - remove(),移除第一次遇到的指定元素 li = ["a","b","c","d","e","city","e"] print(li.remove("e")) print(li) # - del li = ["a","b","c","d","e","city","e"] del li[5] print(li) # - clear() li.clear() print(li)

c [‘a’, ‘b’, ‘d’, ‘e’] None [‘a’, ‘b’, ‘c’, ‘d’, ‘city’, ‘e’] [‘a’, ‘b’, ‘c’, ‘d’, ‘e’, ‘e’] []

#遍历 #（1）元素遍历 li = ["a","b","c"] for i in li: print(i) #(2)索引遍历 li = ["a","b","c"] for i in range(len(li)): print(li[i]) #枚举遍历 # enumerate(),对于一个可迭代的/可遍历的对象（如列表、字符串等）， # enumerate() 将其组成一个索引序列，利用它，我们可以同时获得索引和值 li = ["a","b","c"] for i in enumerate(li,2): print(i) li = ["a","b","c"] for index,value in enumerate(li[:2],2): print(index,value)

(2, ‘a’) (3, ‘b’) (4, ‘c’) 2 a 3 b

#堆和栈，用列表实现 # - 计数，count(),查找元素出现的次数 # - 反转，reverse() li = list("abcd") print(li) li.reverse() print(li)

[‘a’, ‘b’, ‘c’, ‘d’] [‘d’, ‘c’, ‘b’, ‘a’]

# - 排序，sort() li = list("abcd") li.sort() print(li) li.sort(reverse=True) print(li)

[‘a’, ‘b’, ‘c’, ‘d’] [‘d’, ‘c’, ‘b’, ‘a’]

深浅拷贝

import copy a = [1,2,3,['a','b']] #原始对象 b = a #赋值，传对象的引用 c = copy.copy(a) #对象拷贝，浅拷贝 #也可以表示成 c = a[:] d = copy.deepcopy(a) #对象拷贝，深拷贝 a.append(4) #修改对象a a[3].append('c') #修改对象a中['a','b']数组对象 print(a) print(b) print(c) print(d)

浅拷贝只引用了一级对象（里层[复杂子对象]的还是能改）

深拷贝完全独立的两个东西。

列表解析式

li = [] for x in range(10): li.append(x) print(li) print([x**2 for x in range(10) if x%2==0])

[0, 1, 2, 3, 4, 5, 6, 7, 8, 9] [0, 4, 16, 36, 64]

#格式：# python# [表达式 for 迭代元素 in 可迭代对象]#

实现原理：

迭代[可迭代对象]中的每一个元素

每迭代一次的结果赋值给对应的迭代元素，在通过表达式运算得到一个新的值

最后所有通过表达式计算的值以一个列表的形式返回

#三目运算符 y=10 x=y+1 if y>10 else y-1 print(x) 带过滤功能格式 ​```python [exp for iter_val in iter if if_condtion] ​``` li = [] for iter_val in iter: if if_condition: li.append(iter_val) print(li) name = ["Tom", "Jack", "Lucy"] subject = ["python", "java", "c", "c++"] li = [] for i in name: for j in subject: li.append([i,j]) print(li) print([[i,j] for i in name for j in subject])

[[‘Tom’, ‘python’], [‘Tom’, ‘java’], [‘Tom’, ‘c’], [‘Tom’, ‘c++’], [‘Jack’, ‘python’], [‘Jack’, ‘java’], [‘Jack’, ‘c’], [‘Jack’, ‘c++’], [‘Lucy’, ‘python’], [‘Lucy’, ‘java’], [‘Lucy’, ‘c’], [‘Lucy’, ‘c++’]] [[‘Tom’, ‘python’], [‘Tom’, ‘java’], [‘Tom’, ‘c’], [‘Tom’, ‘c++’], [‘Jack’, ‘python’], [‘Jack’, ‘java’], [‘Jack’, ‘c’], [‘Jack’, ‘c++’], [‘Lucy’, ‘python’], [‘Lucy’, ‘java’], [‘Lucy’, ‘c’], [‘Lucy’, ‘c++’]]

元组

有序可重复不可更改

元组的创建

空元组的创建，不能添加元素

单元素组的创建，需要在单元素后面添加逗号

多元素组的创建，包含多种数据类

（1）拼接

（2）重复

（3）索引（偏移） 切片

元组不能增减，可以删。

tp = ("a","b","c") print("a" in tp)# 最大值、最小值 print(max(tp),min(tp))

True c a

三种遍历方式

#遍历 tp = ("a","b","c") for i in tp: print(i,end=" ") print() #索引遍历 tp = ("a","b","c") for i in range(len(tp)): print(tp[i],end=" ") print() # #枚举遍历 tp = ["a","b","c"] for i in enumerate(tp): print(i)

a b c a b c (0, ‘a’) (1, ‘b’) (2, ‘c’)