文章目录
- python 基础课程第三天
python 基础课程第三天
字符串
可变字符串
>>> s="hello,sxt"
>>> import io
>>> sio=io.StringIO(s)
>>> sio
<_io.StringIO object at 0x00000191A0869EE8>
>>> sio.getvalue()
'hello,sxt'
>>> sio.getvalue()
'hello,sxt'
>>> sio.seek(7)
7
>>> sio.write("g")
1
>>> sio.getvalue()
'hello,sgt'
>>> sio.seek(1)
1
>>> sio.write("a")
1
>>> sio.getvalue()
'hallo,sgt'
>>>
基本运算符
>>> a=4
>>> 3<a<10
True
>>> a=0b11001
>>> b=0b01000
>>> a
25
>>> b
8
>>> c=a|b
>>> c
25
>>> bin(c)
'0b11001'
>>> bin(a&b)
'0b1000'
>>> bin(a^b)
'0b10001'
>>> a=3
>>> a<<1
6
>>> aa<<2
Traceback (most recent call last):
File "<pyshell#13>", line 1, in <module>
aa<<2
NameError: name 'aa' is not defined
>>> a<<2
12
>>> b=8
>>> b>>1
4
>>> b>>2
2
>>> b>>3
1
>>> b>>4
0
>>> 3+2
5
复合赋值运算符
运算符优先级
- 乘除优先加减
- 位运算和算术运算>比较运算符>赋值运算符>逻辑运算符
【操作】使用 python 表示数学式：
>>> (5+10*x)/5-13*(y-1)*(a+b)/x+9*(5/x+(12+x)/y)
序列
列表简介
列表对象的常用方法汇总如下：
列表的创建
基本语法[]创建
list()创建
range()创建整数列表
推导式生成列表(简介一下，重点在for 循环后讲)
>>> a=[20,30,40,"gaoqi"]
>>> a[0]
20
>>> a[3]
'gaoqi'
>>> a=[]
>>> a.append(20)
>>> a
[20]
>>> a=list()
>>> a
[]
>>> a=list("gaoqi")
>>> a
['g', 'a', 'o', 'q', 'i']
>>> range(10)
range(0, 10)
>>> a=range(10)
>>> type(a)
<class 'range'>
>>> list(a)
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> list(range(10))
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> list(range(0,10,1))
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> list(range(3,20,2))
[3, 5, 7, 9, 11, 13, 15, 17, 19]
>>> list(range(20,3,-1))
[20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4]
>>> list(range(-10,-33,-1))
[-10, -11, -12, -13, -14, -15, -16, -17, -18, -19, -20, -21, -22, -23, -24, -25, -26, -27, -28, -29, -30, -31, -32]
>>> a=[x*2 for x in range(10)]
>>> a
[0, 2, 4, 6, 8, 10, 12, 14, 16, 18]
>>> a=[x*2 for x in range(100)]
>>> a
[0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, 60, 62, 64, 66, 68, 70, 72, 74, 76, 78, 80, 82, 84, 86, 88, 90, 92, 94, 96, 98, 100, 102, 104, 106, 108, 110, 112, 114, 116, 118, 120, 122, 124, 126, 128, 130, 132, 134, 136, 138, 140, 142, 144, 146, 148, 150, 152, 154, 156, 158, 160, 162, 164, 166, 168, 170, 172, 174, 176, 178, 180, 182, 184, 186, 188, 190, 192, 194, 196, 198]
>>> a=[x*2 for x in range(100) if x%9==0]
>>> a
[0, 18, 36, 54, 72, 90, 108, 126, 144, 162, 180, 198]
>>>
列表元素的增加
append()方法
>>> a=[20,40]
>>> a.append(100)
>>> a
[20, 40, 100]
>>> a.append(200)
>>> a
[20, 40, 100, 200]
+运算符操作
>>> id(a)
2301963635080
>>> a=a+[50]
>>> a
[20, 40, 100, 200, 50]
>>> id(a)
2301994994568
extend()方法
>>> a=[20,40]
>>> id(a)
2301963634504
>>> a.extend([100,200])
>>> a
[20, 40, 100, 200]
>>> id(a)
2301963634504
insert()插入元素
>>> a=[10,20,30,40]
>>> a.insert(2,100)
>>> a
[10, 20, 100, 30, 40]
乘法扩展
>>> a="sxt"*3
>>> a
'sxtsxtsxt'
>>> a=[20,30]
>>> a
[20, 30]
>>> a*3
[20, 30, 20, 30, 20, 30]
>>>
列表元素的删除
del 删除
>>> A=[100,200,888,300,400]
>>> del A[2]
>>> A
[100, 200, 300, 400]
pop()方法
>>> a=[10,20,30,40,50]
>>> b=a.pop()
>>>
>>> b
50
>>> a
[10, 20, 30, 40]
>>> c=a.pop(1)
>>> c
20
>>> a
[10, 30, 40]
remove()方法
>>> a=["aa","bb","gao","cc","dd","gao"]
>>> a
['aa', 'bb', 'gao', 'cc', 'dd', 'gao']
>>> a.remove("gao")
>>> a
['aa', 'bb', 'cc', 'dd', 'gao']
>>> a.remove("asdasf")
Traceback (most recent call last):
File "<pyshell#16>", line 1, in <module>
a.remove("asdasf")
ValueError: list.remove(x): x not in list
>>>
列表元素访问和计数
通过索引直接访问元素
>>> a=[10,20,30,40,50,20,30,20,30]
>>> a[2]
30
>>> a[10]
Traceback (most recent call last):
File "<pyshell#7>", line 1, in <module>
a[10]
IndexError: list index out of range
>>>
index()获得指定元素在列表中首次出现的索引
>>> a=[10,20,30,40,50,20,30,20,30]
>>> a.index(20)
1
>>> a.index(20,3)
5
>>> a.index(30,5,7)
6
>>>
count()获得指定元素在列表中出现的次数
>>> a=[100,200,100,300]
>>> a.count(100)
2
len()返回列表长度
>>> a=[10,20,30]
>>> len(a)
3
>>>
成员资格判断
>>> "a" in "abc"
True
>>> 10 in [10,20,30,10]
True
>>> 10 in [1,2,3,4,5]
False
>>> a=[100,200,100,300]
>>> a.count(100)
2
切片操作
>>> a=[10,20,30,40,50,60]
>>> a[:]
[10, 20, 30, 40, 50, 60]
>>> a[1:3:1]
[20, 30]
>>> a[1::2]
[20, 40, 60]
>>> a[1:]
[20, 30, 40, 50, 60]
>>> a[:2:]
[10, 20]
>>> a
[10, 20, 30, 40, 50, 60]
>>> a[-3:]
[40, 50, 60]
>>> a[-3:-2]
[40]
>>> a[::-1]
[60, 50, 40, 30, 20, 10]
>>>
列表的遍历
>>> a=[10,20,30,40,50,60]
>>> for x in a:
print(x)
10
20
30
40
50
60
>>> for x in a:
print(x,end="#")
10#20#30#40#50#60#
>>>
列表排序
修改原列表，不建新列表的排序
>>> a=[20,10,30,40]
>>> id(a)
2254789019720
>>> a.sort()
>>> a
[10, 20, 30, 40]
>>> id(a)
2254789019720
>>> a.sort(reverse=True)
>>> a
[40, 30, 20, 10]
>>> import random
>>> random.shuffle(a)
>>> a
[20, 10, 30, 40]
>>> random.shuffle(a)
>>> a
[40, 30, 20, 10]
>>>
建新列表的排序
>>> a=[20,10,30,40]
>>> id(a)
2254793598792
>>> a=sorted(a)
>>> a
[10, 20, 30, 40]
>>> id(a)
2254789019720
>>> a=[20,10,30,40]
>>> id(a)
2254793598408
>>> b=sorted(a)
>>> b
[10, 20, 30, 40]
>>> id(a)
2254793598408
>>> id(b)
2254788814856
>>> c=sorted(a,reverse=True)
>>> c
[40, 30, 20, 10]
>>> id(c)
2254793599048
>>>
reversed()返回迭代器
>>> a=[20,10,30,40]
>>> c=reversed(a)
>>> c
<list_reverseiterator object at 0x0000020CFBE7CB08>
>>> list(c)
[40, 30, 10, 20]
>>> list(c)
[]
>>>
列表相关的其他内置函数汇总
max 和min
>>> a = [3,10,20,15,9]
>>> max(a)
20
>>> min(a)
3
>>>
sum
>>> a = [3,10,20,15,9]
>>> sum(a)
57
>>>
多维列表
二维列表
>>> a=[
["高小一",18,30000,"北京"],
["高小二",19,20000,"上海"],
["高小五",20,10000,"深圳"]
]
>>> a
[['高小一', 18, 30000, '北京'], ['高小二', 19, 20000, '上海'], ['高小五', 20, 10000, '深圳']]
>>> a[0]
['高小一', 18, 30000, '北京']
>>> a[0][3]
'北京'
元组tuple
- 索引访问
- 切片操作
- 连接操作
- 成员关系操作
- 比较运算操作
- 计数：元组长度len()、最大值max()、最小值min()、求和sum()等。
元组的创建
>>> a=(10,20,30)
>>> type(a)
<class 'tuple'>
>>> a=10,20,30
>>> type(a)
<class 'tuple'>
>>> b=(20)
>>> type(b)
<class 'int'>
>>> b=(20,)
>>> type(b)
<class 'tuple'>
>>> b=20,
>>> type(b)
<class 'tuple'>
>>> b=tuple("abcd")
>>> b
('a', 'b', 'c', 'd')
>>> b=list("abcd")
>>> b
['a', 'b', 'c', 'd']
>>> b=tuple(range(3))
>>> b
(0, 1, 2)
>>> b=tuple([30,40,50])
>>> b
(30, 40, 50)
>>> del b
>>> b
Traceback (most recent call last):
File "<pyshell#19>", line 1, in <module>
b
NameError: name 'b' is not defined
>>>
元组的元素访问和计数
>>> a=[20,30,40]
>>> a[1]
30
>>> a[1]=100
>>> a
[20, 100, 40]
>>> a=(20,30,40)
>>> a[1]
30
>>> a[1]=100
Traceback (most recent call last):
File "<pyshell#29>", line 1, in <module>
a[1]=100
TypeError: 'tuple' object does not support item assignment
>>> b=(30,20,40)
>>> sorted(b)
[20, 30, 40]
zip
>>> a=[10,20,30]
>>> b=[40,50,60]
>>> c=[70,80,90]
>>> d=zip(a,b,c)
>>> d
<zip object at 0x00000226699C1508>
>>> list(d)
[(10, 40, 70), (20, 50, 80), (30, 60, 90)]
>>>
生成器推导式创建元组
>>> s=(x*2 for x in range(5))
>>> s
<generator object <genexpr> at 0x000001D1137B5248>
>>> tuple(s)
(0, 2, 4, 6, 8)
>>> tuple(s)
()
>>> s=(x*2 for x in range(5))
>>> s.__next__()
0
>>> s.__next__()
2
>>> s.__next__()
4
>>> s.__next__()
6
>>> s.__next__()
8
>>> s.__next__()
Traceback (most recent call last):
File "<pyshell#10>", line 1, in <module>
s.__next__()
StopIteration
>>>
