标签：打印 中间 比较 第一个 add while 可变 显示 blog
变量的组成:
变量由变量名,赋值符号,变量值三部分组成,变量还分类型.
变量名→n = 1←变量值
↑
赋值符号
比较方法:
身份比较:比较的是变量值的id
>>> x = 300 >>> id(x) 46137936 >>> y = 300 >>> id(y) 46137984 >>> x is y False >>>
值比较:比较两个变量值
>>> x = 300 >>> y = 300 >>> id(x) 54002288 >>> id(y) 54002352 >>> x == y True >>>
类型比较:比较两个变量的类型
>>> x = 300 >>> y = 300 >>> type(x) <class ‘int‘> >>> type(y) <class ‘int‘> >>> type(x) is type(y) True >>>
变量赋值操作(补充):
>>> x = 1 >>> y = 2 >>> x,y = y,x >>> x 2 >>> y 1 >>>
增量赋值:
>>> s = ‘hello‘ >>> a,b,c,d,e = s >>> a ‘h‘ >>> b ‘e‘ >>> c ‘l‘ >>> d ‘l‘ >>> e ‘o‘ >>> a,*_,b = s >>> a ‘h‘ >>> b ‘o‘ >>>
分类:
一：可变不可变
可变：列表，字典
不可变：数字，字符串，元组
二：存放值的个数
一个值：数字，字符串
多个值(容器类型)：列表，元组，字典
三：取值方式
直接取值：数字
序列类型：字符串，元组，列表
映射类型：字典
可变或者不可变的定义:在id和type不变的情况下,值可变的数据是可变类型.id,type,value都不可变的是不可变类型
列表list:
特性:list中的元素可以随意删除增加且list的id和type不会改变,ist是一种可变类型.列表中的所有元素可以是 int 可以是 str 也可以是list(子列表).list中的值是有序的.
定义一个list:
l = [1,‘abc‘,[3,‘a‘]]
取值: 通过索引取值
print(l[0],l[2][0])
循环: liang
#! /usr/bin/env python # -*- coding: utf-8 -*- l=[1,2,3,[4,5]] count=0 while count < len(l): print(l[count]) count+=1 l=[1,2,3,[4,5]] for count in range(len(l)): if type(l[count]) is list: for i in range(len(l[count])): print(l[count][i]) else: print(l[count])
列表常用操作:
切片:
l = [‘hello‘,12,‘abc‘,343,‘ppp‘]
print(l[1:3])
D:\Python\Python36-32\python.exe E:/Python/123.py
[12, ‘abc‘]
Process finished with exit code 0
追加:
l = [‘hello‘,12,‘abc‘,343,‘ppp‘]
l.append(‘add_1‘)
l.append(‘add_2‘)
l.append(‘add_3‘)
print(l)
D:\Python\Python36-32\python.exe E:/Python/123.py [‘hello‘, 12, ‘abc‘, 343, ‘ppp‘, ‘add_1‘, ‘add_2‘, ‘add_3‘] Process finished with exit code 0
插入:
l = [‘hello‘,12,‘abc‘,343,‘ppp‘]
l.insert(0,‘insert_1‘)
print(l)
l.insert(2,‘insert_2‘)
print(l)
l.insert(4,‘insert_3‘)
print(l)
D:\Python\Python36-32\python.exe E:/Python/123.py [‘insert_1‘, ‘hello‘, 12, ‘abc‘, 343, ‘ppp‘] [‘insert_1‘, ‘hello‘, ‘insert_2‘, 12, ‘abc‘, 343, ‘ppp‘] [‘insert_1‘, ‘hello‘, ‘insert_2‘, 12, ‘insert_3‘, ‘abc‘, 343, ‘ppp‘] Process finished with exit code 0
删除:
l = [‘hello‘,12,‘abc‘,343,‘ppp‘]
print(l)
l.pop()
print(l)
l.pop(2)
print(l)
D:\Python\Python36-32\python.exe E:/Python/123.py [‘hello‘, 12, ‘abc‘, 343, ‘ppp‘] [‘hello‘, 12, ‘abc‘, 343] [‘hello‘, 12, 343] Process finished with exit code 0
包含:
l = [‘hello‘,12,‘abc‘,343,‘ppp‘]
print(12 in l)
print(‘abc‘ in l)
print(‘12‘ in l)
D:\Python\Python36-32\python.exe E:/Python/123.py
True
True
False
Process finished with exit code 0
显示索引位置:
l = [‘hello‘,12,‘abc‘,343,‘ppp‘]
print(l)
print(l.index(12))
print(l.index(‘hello‘))
D:\Python\Python36-32\python.exe E:/Python/123.py [‘hello‘, 12, ‘abc‘, 343, ‘ppp‘] 1 0 Process finished with exit code 0
计算元素个数:
l = [‘hello‘,12,‘abc‘,343,‘ppp‘]
l.append(‘hello‘)
print(l)
print(l.count(‘hello‘))
D:\Python\Python36-32\python.exe E:/Python/123.py [‘hello‘, 12, ‘abc‘, 343, ‘ppp‘, ‘hello‘] 2 Process finished with exit code 0
扩展列表:
l = [‘hello‘,12,‘abc‘,343,‘ppp‘]
l.extend([1,2,3,4]) #只能扩展列表,如果需要向列表添加 字典和元组需要使用append
print(l)
D:\Python\Python36-32\python.exe E:/Python/123.py [‘hello‘, 12, ‘abc‘, 343, ‘ppp‘, 1, 2, 3, 4] Process finished with exit code 0
移除元素: 通过元素名来移除元素
l = [‘hello‘,12,‘abc‘,343,‘ppp‘]
l.remove(‘abc‘) #如果列表有多个元素,则只移除第一个
print(l)
D:\Python\Python36-32\python.exe E:/Python/123.py [‘hello‘, 12, 343, ‘ppp‘] Process finished with exit code 0
顺序排列:
l=[2,3,1]
l.sort()
print(l)
D:\Python\Python36-32\python.exe E:/Python/123.py [1, 2, 3] Process finished with exit code 0
反转列表:
l=[‘a‘,‘c‘,‘alex‘]
l.reverse()
print(l)
D:\Python\Python36-32\python.exe E:/Python/123.py [‘alex‘, ‘c‘, ‘a‘] Process finished with exit code 0
元组:
特性:元组内的所有元素不能更改,元素可以是任意数据类型
元组中可以包含list,元组中的list中的元素是可以更改的.当然list中也可以有元组.
定义元组:
a = (‘1‘,‘2‘,‘3‘,[‘s‘,‘b‘])
更改元组中list的元素:
a[3][0] = abc
取值:
print(a[0])
循环:
t = (‘a‘,1,‘b‘,1,(3,4))
n = 0
while n < len(t):
print(t[n])
n += 1
for i in range(len(t)):
print(t[i])
元组的常用操作:
计数:
t = (‘a‘,1,‘b‘,1,(3,4))
print(t.count(1))
D:\Python\Python36-32\python.exe E:/Python/123.py 2 Process finished with exit code 0
索引位置:
t = (‘a‘,1,‘b‘,1,(3,4))
print(t.index(‘b‘))
D:\Python\Python36-32\python.exe E:/Python/123.py 2 Process finished with exit code 0
切片:
t=(‘a‘,1,‘b‘,1,(3,4))
print(t[1:3])
D:\Python\Python36-32\python.exe E:/Python/123.py (1, ‘b‘) Process finished with exit code 0
包含:
t=(‘a‘,1,‘b‘,1,(3,4))
print(‘a‘ in t)
D:\Python\Python36-32\python.exe E:/Python/123.py
True
Process finished with exit code 0
标签：打印 中间 比较 第一个 add while 可变 显示 blog
原文地址：http://www.cnblogs.com/ldsly/p/6965239.html
