- 基本数据类型
1、数字
int（整型）
在32位机器上，整数的位数为32位，取值范围为-2**31～2**31-1，即-2147483648～2147483647
在64位系统上，整数的位数为64位，取值范围为-2**63～2**63-1，即-9223372036854775808～9223372036854775807
1 1）int --> string
2 str是保留关键字，
3 >>>a = 10
4 >>>str1 = str(a)
5
6 2)string --> int
7 >>>x = ""
8 >>>y = int(x) 1 >>> lists = ['a', 'b', 'e', 'c', 'd', 'a']
2 >>> print '列表list转换为str:', ''.join(lists)
3 结果：
4 列表list转换为str: abecda
5
6 >>>strs = 'hongten'
7 >>>print '序列strs转换为list:', list(strs)
8 结果：
9 序列strs转换为list：['h', 'o', 'n', 'g', 't', 'e', 'n']
10
11 >>>print '列表list转换为tuple:', tuple(lists)
12 结果：
13 列表list转换为tuple:（'h', 'o', 'n', 'g', 't', 'e', 'n'）
14
15 >>>print '整数转换为字符chr:', chr(67)
16 结果：
17 整数转换为字符chr:'C'
18
19 >>>print('字符chr转换为整数:', ord('C'))
20 结果：
21 字符chr转换为整数:67
22
23 >>>print('整数转16进制数:', hex(12))
24 结果：：
25 整数转16进制数:'0xc'
26
27 >>>print('整数转8进制数:', oct(12))
28 结果：
29 整数转8进制数:''
2、布尔值
在计算机内部，python使用1来表示True，而使用0来表示False。可以使用int数将布尔值转换为一个整数。
实例：
>>>print(int(True))
>>>1 >>>print(int(False))
>>>0
也可以用bool函数将一个数字值转换成一个布尔值。如果值为0，这个函数返回False; 否则，这个函数总是返回True。
实例：
>>>print(bool(0))
>>>False >>>print(bool(1))
>>>True
3、字符串
a、处理字符串的函数
>>> s = "Welcome"
>>> len(s)
7
>>> max(s)
'o'
>>> min(s)
'W'
b、下标运算符
>>> s = "Welcome"
>>>for i in range(0, len(s), 2):
print(s[i], end = '')
>>>Wloe >>>s = "Welcome"
>>>s[-1]
'e'
>>>s[-2]
'm'
c、截取运算符
>>> s = "Welcome"
>>> s[1:4]
'elc'
>>> s[ :6]
'Welcom'
>>> s[4: ]
'ome'
>>> s[1:-1]
'elcom'
d、in和not in 运算符
>>> s = "Welcome"
>>> 'come' in s
True
>>> 'come' not in s
False
e、比较字符串
>>> "green" == "glow"
False
>>> "green" != "glow"
True
>>> "green" > "glow"
True
>>> "green" < "glow"
False
>>> "green" <= "glow"
False
f、搜索字串
>>> s = "welcome to python"
>>> s.endswith('thon')
True
>>> s.startswith("good")
False
>>> s.find("come")
3
>>> s.find("become")
-1
>>> s.find("o")
4
>>> s.rfind("o")
15
>>> s.count("o")
3
g、转换字符串
>>> s = "welcome to python"
>>> s1 = s.capitalize()
>>> s1
'Welcome to python'
>>> s2 = s.title()
>>> s2
'Welcome To Python'
>>> s = "New England"
>>> s3 = s.lower()
>>> s3
'new england'
>>> s4 = s.upper()
>>> s4
'NEW ENGLAND'
>>> s5 = s.swapcase()
>>> s5
'nEW eNGLAND'
>>> s6 = s.replace("England", "Haven")
>>> s6
'New Haven'
>>> s
'New England'
H、删除字符串的空格
>>> s = " Welcome to Python\t"
>>> s1 = s.lstrip()
>>> s1
'Welcome to Python\t'
>>> s2 = s.rstrip()
>>> s2
' Welcome to Python'
>>> s3 = s.strip()
>>> s3
'Welcome to Python'
I、格式化字符串
>>> s = "Welcome"
>>> s1 = s.center(11)
>>> s1
' Welcome '
>>> s2 = s.ljust(11)
>>> s2
'Welcome '
>>> s3 = s.rjust(11)
>>> s3
' Welcome'
4、列表
a、列表使用的函数
>>> list = [2,3,4,1,32]
>>> len(list)
5
>>> max(list)
32
>>> min(list)
1
>>> sum(list)
42
b、下标运算符
>>> list = [2,3,5,2,33,21]
>>> list[-1]
21
>>> list[-3]
2
c、列表截取
>>> list = [2,3,5,2,33,21]
>>> list[2:4]
[5, 2]
>>> list[:2]
[2, 3]
>>> list[3:]
[2, 33, 21]
>>> list[1:-3]
[3, 5]
>>> list[-4:-2]
[5, 2]
d、列表方法
>>> list = [2,3,4,1,32,4]
>>> list.append(19)
>>> list
[2, 3, 4, 1, 32, 4, 19]
>>> list.count(4)
2
>>> list2 = [99,54]
>>> list.extend(list2)
>>> list
[99, 25, 54, 99, 54, 99, 54]
>>> list.insert(1,25)
>>> list
[99, 25, 25, 54, 99, 54, 99, 54]
>>> list1 = [2,25,3,4,1,32,4,1,32,4,19,99,54]
>>> list.pop(2)
25
>>> list1
[2, 25, 4, 1, 32, 4, 1, 32, 4, 19, 99, 54]
>>> list1 = [2,25,3,4,1,32,4,1,32,4,19,99,54]
>>> list.pop(2)
25
>>> list
[99, 25, 54, 99, 54, 99, 54]
>>> list1
[2, 25, 3, 4, 1, 32, 4, 1, 32, 4, 19, 99, 54]
>>>
>>>
>>> list1.pop(2)
3
>>> list1
[2, 25, 4, 1, 32, 4, 1, 32, 4, 19, 99, 54]
>>> list1.pop()
54
>>> list1
[2, 25, 4, 1, 32, 4, 1, 32, 4, 19, 99]
>>> list1.remove(32)
>>> list1
[2, 25, 4, 1, 4, 1, 32, 4, 19, 99]
>>> list1.reverse()
>>> list1
[99, 19, 4, 32, 1, 4, 1, 4, 25, 2] >>> list1.sort()
>>> list1
[1, 1, 2, 4, 4, 4, 19, 25, 32, 99]
e、enumerate遍历列表
使用如下的方式遍历一个列表，但是缺点是无法读取索引index。
>>> a = [3,4,5,2,3,7,8,9]
>>> for i in a:
... print i
...
3
4
5
2
3
7
8
9下面两种方法改进，如下举例：
>>> for index,item in enumerate(a):
... print index,item
...
0 3
1 4
2 5
3 2
4 3
5 7
6 8
7 9
>>>
>>>
>>> for i in range(len(a)):
... print i,a[i]
...
0 3
1 4
2 5
3 2
4 3
5 7
6 8
7 9
>>>
5、元组
元组跟列表类似，但是元组中的元素是固定的，也就是说，一旦一个元组被创建，就无法对元组中的元素进行添加、删除、替代或重新排序。
>>> tuple1 = ("green", "red", "blue")
>>> print tuple1
('green', 'red', 'blue')
>>> tuple2 = tuple([7,1,2,23,4,5])
>>> print tuple2
(7, 1, 2, 23, 4, 5)
6、字典
字典是一个存储键值对集合的容器对象。它通过使用关键字实现快速、删除和更新值。
如创建字典语句：
students = {”111-34-3434“:"John", "132-56-6290":"Peter"}
a、添加、删除举例：
>>> students = {"111-34-3434" : "John", "132-56-6290" : "Peter"}
>>> students["234-56-9010"] = "Susan" #从字典添加条目
>>> students["234-56-9010"]
'Susan'
>>> del students["234-56-9010"] #从字典删除一个条目
b、循环条目：
>>>students = {'111-34-3434': 'John Smith', '132-56-6290': 'Peter'}
>>> for key in students:
... print(key + ":" + str(students[key]))
...
111-34-3434:John Smith
132-56-6290:Peter
c、len函数：
>>>students = {'111-34-3434': 'John Smith', '132-56-6290': 'Peter'}
>>>len(students)
2
d、检测一个关键字是否在字典中：
>>>students = {'111-34-3434': 'John Smith', '132-56-6290': 'Peter'}
>>> "111-34-3434" in students
True
>>> "998-34-3434" in students
False
>>>
e、相等性检测：
>>> d1 = {"red":41, "blue":3}
>>> d2 = {"blue":3, "red":41}
>>> d1 == d2
True
>>> d1 != d2
False
>>>
f、字典方法：
>>> students = {"111-34-3434":"John", "132-56-6290":"Peter"}
>>> tuple(students.keys())
('111-34-3434', '132-56-6290')
>>> tuple(students.values())
('John', 'Peter')
>>> tuple(students.items())
(('111-34-3434', 'John'), ('132-56-6290', 'Peter'))
>>> students.get("111-34-3434")
'John'
>>> print(students.get("999-334-3434"))
None
>>> students.pop("111-34-3434")
'John'
>>> students
{'132-56-6290': 'Peter'}
>>> students.clear()
>>> students
{}
>>>
dic = {'k1' : 123,'k2' : 456,'k4' : 111}
n = dic.fromkeys(['k1','k2','k3'],[])
print(n)
n['k1'].append('x')
print(n) 运行结果如下：
{'k2': [], 'k1': [], 'k3': []}
{'k2': ['x'], 'k1': ['x'], 'k3': ['x']} dic = {'k1' : 123,'k2' : 456,'k4' : 111}
n = dic.fromkeys(['k1','k2','k3'],'alex')
print(n) 运行结果如下：
{'k3': 'alex', 'k1': 'alex', 'k2': 'alex'} li = [11,22,44]
new_dict = dict(enumerate(li))
print(new_dict) 运行结果如下：
{0: 11, 1: 22, 2: 44} li = [11,22,44]
new_dict = dict(enumerate(li,10))
print(new_dict) 运行结果如下：
{10: 11, 11: 22, 12: 44} t = (11,22,['alex',{'k1':"v1"}])
t[2][1]['k2'] = 123
print(t) 运行结果如下：
(11, 22, ['alex', {'k1': 'v1', 'k2': 123}]) t = (11,22,['alex',{'k1':"v1"}])
t[2][1].update({'k2':123})
print(t) 运行结果如下：
(11, 22, ['alex', {'k1': 'v1', 'k2': 123}])
