52个python基础代码，你全都知道吗？_python基础代码大全

Hello，大家好，我是程序汪小陈

今天，我将为大家展示python基础小例子，帮助大家加深记忆，列举52个例子，快来看看吧~

1 求绝对值

绝对值或复数的模

In [1]: abs(-6)
Out[1]: 6

2 元素都为真

接受一个迭代器，如果迭代器的所有元素都为真，那么返回True，否则返回False

In [2]: all([1,0,3,6])
Out[2]: False
 
In [3]: all([1,2,3])
Out[3]: True

3 元素至少一个为真 

接受一个迭代器，如果迭代器里至少有一个元素为真，那么返回True，否则返回False

In [4]: any([0,0,0,[]])
Out[4]: False
 
In [5]: any([0,0,1])
Out[5]: True

4 ascii展示对象  

调用对象的__repr__() 方法，获得该方法的返回值，如下例子返回值为字符串

In [1]: class Student():
   ...:     def __init__(self,id,name):
   ...:         self.id = id
   ...:         self.name = name
   ...:     def __repr__(self):
   ...:         return 'id = '+self.id +', name = '+self.name
   ...: 
   ...: 
 
In [2]: xiaoming = Student(id='001',name='xiaoming')
 
In [3]: print(xiaoming)
id = 001, name = xiaoming
 
In [4]: ascii(xiaoming)
Out[4]: 'id = 001, name = xiaoming'

5 十转二

将十进制转换为二进制

In [1]: bin(10)
Out[1]: '0b1010'

6 十转八

将十进制转换为八进制

In [1]: oct(9)
Out[1]: '0o11'

7 十转十六

将十进制转换为十六进制

In [1]: hex(15)
Out[1]: '0xf'

8 判断是真是假  

测试一个对象是True, 还是False.

In [1]: bool([0,0,0])
Out[1]: True
 
In [2]: bool([])
Out[2]: False
 
In [3]: bool([1,0,1])
Out[3]: True

9 字符串转字节  

将一个字符串转换成字节类型

In [1]: s = "apple"
 
In [2]: bytes(s,encoding='utf-8')
Out[2]: b'apple'
 

10 转为字符串  

将字符类型、数值类型等转换为字符串类型

In [1]: i = 100
 
In [2]: str(i)
Out[2]: '100'
 

11 是否可调用  

判断对象是否可被调用，能被调用的对象就是一个callable 对象，比如函数 str, int 等都是可被调用的，但是例子4 中xiaoming实例是不可被调用的：

In [1]: callable(str)
Out[1]: True
 
In [2]: callable(int)
Out[2]: True
 
In [3]: xiaoming
Out[3]: id = 001, name = xiaoming
 
In [4]: callable(xiaoming)
Out[4]: False
 

如果想让xiaoming能被调用 xiaoming(), 需要重写Student类的__call__方法：

In [1]: class Student():
    ...:     def __init__(self,id,name):
    ...:         self.id = id
    ...:         self.name = name
    ...:     def __repr__(self):
    ...:         return 'id = '+self.id +', name = '+self.name
    ...:     def __call__(self):
    ...:         print('I can be called')
    ...:         print(f'my name is {self.name}')
    ...: 
    ...: 
 
In [2]: t = Student('001','xiaoming')
 
In [3]: t()
I can be called
my name is xiaoming
 
 

12 十转ASCII

查看十进制整数对应的ASCII字符

In [1]: chr(65)
Out[1]: 'A'
 

13 ASCII转十

查看某个ASCII字符对应的十进制数

In [1]: ord('A')
Out[1]: 65
 

14 静态方法 

classmethod 装饰器对应的函数不需要实例化，不需要 self参数，但第一个参数需要是表示自身类的 cls 参数，可以来调用类的属性，类的方法，实例化对象等。

In [1]: class Student():
    ...:     def __init__(self,id,name):
    ...:         self.id = id
    ...:         self.name = name
    ...:     def __repr__(self):
    ...:         return 'id = '+self.id +', name = '+self.name
    ...:     @classmethod
    ...:     def f(cls):
    ...:         print(cls)
 

15 执行字符串表示的代码

将字符串编译成python能识别或可执行的代码，也可以将文字读成字符串再编译。

In [1]: s  = "print('helloworld')"
    
In [2]: r = compile(s,"<string>", "exec")
    
In [3]: r
Out[3]: <code object <module> at 0x0000000005DE75D0, file "<string>", line 1>
    
In [4]: exec(r)
helloworld
 

16 创建复数

创建一个复数

In [1]: complex(1,2)
Out[1]: (1+2j)
 

17 动态删除属性  

删除对象的属性

In [1]: delattr(xiaoming,'id')
 
In [2]: hasattr(xiaoming,'id')
Out[2]: False
 

18 转为字典  

创建数据字典

In [1]: dict()
Out[1]: {}
 
In [2]: dict(a='a',b='b')
Out[2]: {'a': 'a', 'b': 'b'}
 
In [3]: dict(zip(['a','b'],[1,2]))
Out[3]: {'a': 1, 'b': 2}
 
In [4]: dict([('a',1),('b',2)])
Out[4]: {'a': 1, 'b': 2}
 

19 一键查看对象所有方法 

不带参数时返回当前范围内的变量、方法和定义的类型列表；带参数时返回参数的属性，方法列表。

In [96]: dir(xiaoming)
Out[96]:
['__class__',
 '__delattr__',
 '__dict__',
 '__dir__',
 '__doc__',
 '__eq__',
 '__format__',
 '__ge__',
 '__getattribute__',
 '__gt__',
 '__hash__',
 '__init__',
 '__init_subclass__',
 '__le__',
 '__lt__',
 '__module__',
 '__ne__',
 '__new__',
 '__reduce__',
 '__reduce_ex__',
 '__repr__',
 '__setattr__',
 '__sizeof__',
 '__str__',
 '__subclasshook__',
 '__weakref__',
 
 'name']
 

20 取商和余数  

分别取商和余数

In [1]: divmod(10,3)
Out[1]: (3, 1)
 

21 枚举对象  

返回一个可以枚举的对象，该对象的next()方法将返回一个元组。

In [1]: s = ["a","b","c"]
    ...: for i ,v in enumerate(s,1):
    ...:     print(i,v)
    ...:
1 a
2 b
3 c
 

22 计算表达式

将字符串str 当成有效的表达式来求值并返回计算结果取出字符串中内容

In [1]: s = "1 + 3 +5"
    ...: eval(s)
    ...:
Out[1]: 9
 

23 查看变量所占字节数

In [1]: import sys
 
In [2]: a = {'a':1,'b':2.0}
 
In [3]: sys.getsizeof(a) # 占用240个字节
Out[3]: 240
 

24 过滤器  

在函数中设定过滤条件，迭代元素，保留返回值为True的元素：

In [1]: fil = filter(lambda x: x>10,[1,11,2,45,7,6,13])
 
In [2]: list(fil)
Out[2]: [11, 45, 13]
 

25 转为浮点类型 

将一个整数或数值型字符串转换为浮点数

In [1]: float(3)
Out[1]: 3.0
 

如果不能转化为浮点数，则会报ValueError:

In [2]: float('a')
ValueError                                Traceback (most recent call last)
<ipython-input-11-99859da4e72c> in <module>()
----> 1 float('a')
 
ValueError: could not convert string to float: 'a'
 
 

26 字符串格式化 

格式化输出字符串，format(value, format_spec)实质上是调用了value的__format__(format_spec)方法。

In [104]: print("i am {0},age{1}".format("tom",18))
i am tom,age18
 

27 冻结集合  

创建一个不可修改的集合。

In [1]: frozenset([1,1,3,2,3])
Out[1]: frozenset({1, 2, 3})
 

因为不可修改，所以没有像set那样的add和pop方法

28 动态获取对象属性 

获取对象的属性

In [1]: class Student():
   ...:     def __init__(self,id,name):
   ...:         self.id = id
   ...:         self.name = name
   ...:     def __repr__(self):
   ...:         return 'id = '+self.id +', name = '+self.name
 
In [2]: xiaoming = Student(id='001',name='xiaoming')
In [3]: getattr(xiaoming,'name') # 获取xiaoming这个实例的name属性值
Out[3]: 'xiaoming'
 

29 对象是否有这个属性

In [1]: class Student():
   ...:     def __init__(self,id,name):
   ...:         self.id = id
   ...:         self.name = name
   ...:     def __repr__(self):
   ...:         return 'id = '+self.id +', name = '+self.name
 
In [2]: xiaoming = Student(id='001',name='xiaoming')
In [3]: hasattr(xiaoming,'name')
Out[3]: True
 
In [4]: hasattr(xiaoming,'address')
 

30 返回对象的哈希值  

返回对象的哈希值，值得注意的是自定义的实例都是可哈希的，list, dict, set等可变对象都是不可哈希的(unhashable)

In [1]: hash(xiaoming)
Out[1]: 6139638
 
In [2]: hash([1,2,3])
TypeError                                 Traceback (most recent call last)
<ipython-input-32-fb5b1b1d9906> in <module>()
----> 1 hash([1,2,3])
 
TypeError: unhashable type: 'list'
 

31 一键帮助 

返回对象的帮助文档

In [1]: help(xiaoming)
Help on Student in module __main__ object:
 
class Student(builtins.object)
 |  Methods defined here:
 |
 |  __init__(self, id, name)
 |
 |  __repr__(self)
 |
 |  Data descriptors defined here:
 |
 |  __dict__
 |      dictionary for instance variables (if defined)
 |
 |  __weakref__
 |      list of weak references to the object (if defined)
 

32 对象门牌号 

返回对象的内存地址

In [1]: id(xiaoming)
Out[1]: 98234208
 

33 获取用户输入 

获取用户输入内容

In [1]: input()
aa
Out[1]: 'aa'
 

34 转为整型  

int(x, base =10) , x可能为字符串或数值，将x 转换为一个普通整数。如果参数是字符串，那么它可能包含符号和小数点。如果超出了普通整数的表示范围，一个长整数被返回。

In [1]: int('12',16)
Out[1]: 18
 

35 isinstance

判断object是否为类classinfo的实例，是返回true

In [1]: class Student():
   ...:     def __init__(self,id,name):
   ...:         self.id = id
   ...:         self.name = name
   ...:     def __repr__(self):
   ...:         return 'id = '+self.id +', name = '+self.name
 
In [2]: xiaoming = Student(id='001',name='xiaoming')
 
In [3]: isinstance(xiaoming,Student)
Out[3]: True
 

36 父子关系鉴定

In [1]: class undergraduate(Student):
    ...:     def studyClass(self):
    ...:         pass
    ...:     def attendActivity(self):
    ...:         pass
 
In [2]: issubclass(undergraduate,Student)
Out[2]: True
 
In [3]: issubclass(object,Student)
Out[3]: False
 
In [4]: issubclass(Student,object)
Out[4]: True
 

如果class是classinfo元组中某个元素的子类，也会返回True

In [1]: issubclass(int,(int,float))
Out[1]: True
 

37 创建迭代器类型

使用iter(obj, sentinel), 返回一个可迭代对象, sentinel可省略(一旦迭代到此元素，立即终止)

In [1]: lst = [1,3,5]
 
In [2]: for i in iter(lst):
    ...:     print(i)
    ...:
1
3
5
 

In [1]: class TestIter(object):
    ...:     def __init__(self):
    ...:         self.l=[1,3,2,3,4,5]
    ...:         self.i=iter(self.l)
    ...:     def __call__(self):  #定义了__call__方法的类的实例是可调用的
    ...:         item = next(self.i)
    ...:         print ("__call__ is called,fowhich would return",item)
    ...:         return item
    ...:     def __iter__(self): #支持迭代协议(即定义有__iter__()函数)
    ...:         print ("__iter__ is called!!")
    ...:         return iter(self.l)
In [2]: t = TestIter()
In [3]: t() # 因为实现了__call__，所以t实例能被调用
__call__ is called,which would return 1
Out[3]: 1
 
In [4]: for e in TestIter(): # 因为实现了__iter__方法，所以t能被迭代
    ...:     print(e)
    ...: 
__iter__ is called!!
1
3
2
3
4
5
 

38 所有对象之根

object 是所有类的基类

In [1]: o = object()
 
In [2]: type(o)
Out[2]: object
 

39 打开文件

返回文件对象

In [1]: fo = open('D:/a.txt',mode='r', encoding='utf-8')
 
In [2]: fo.read()
Out[2]: '\ufefflife is not so long,\nI use Python to play.'

mode取值表：

40 次幂

base为底的exp次幂，如果mod给出，取余

In [1]: pow(3, 2, 4)
Out[1]: 1

41 打印

In [5]: lst = [1,3,5]
 
In [6]: print(lst)
[1, 3, 5]
 
In [7]: print(f'lst: {lst}')
lst: [1, 3, 5]
 
In [8]: print('lst:{}'.format(lst))
lst:[1, 3, 5]
 
In [9]: print('lst:',lst)
lst: [1, 3, 5]

42 创建属性的两种方式

返回 property 属性，典型的用法：

class C:
    def __init__(self):
        self._x = None
 
    def getx(self):
        return self._x
 
    def setx(self, value):
        self._x = value
 
    def delx(self):
        del self._x
    # 使用property类创建 property 属性
    x = property(getx, setx, delx, "I'm the 'x' property.")

使用python装饰器，实现与上完全一样的效果代码：

class C:
    def __init__(self):
        self._x = None
 
    @property
    def x(self):
        return self._x
 
    @x.setter
    def x(self, value):
        self._x = value
 
    @x.deleter
    def x(self):
        del self._x

43 创建range序列

1. range(stop)
2. range(start, stop[,step])

生成一个不可变序列：

In [1]: range(11)
Out[1]: range(0, 11)
 
In [2]: range(0,11,1)
Out[2]: range(0, 11)

44 反向迭代器

In [1]: rev = reversed([1,4,2,3,1])
 
In [2]: for i in rev:
     ...:     print(i)
     ...:
1
3
2
4
1

45 四舍五入

四舍五入，ndigits代表小数点后保留几位：

In [11]: round(10.0222222, 3)
Out[11]: 10.022
 
In [12]: round(10.05,1)
Out[12]: 10.1

46 转为集合类型

返回一个set对象，集合内不允许有重复元素：

In [159]: a = [1,4,2,3,1]
 
In [160]: set(a)
Out[160]: {1, 2, 3, 4}

47 转为切片对象

class slice(start, stop[, step])

返回一个表示由 range(start, stop, step) 所指定索引集的 slice对象，它让代码可读性、可维护性变好。

In [1]: a = [1,4,2,3,1]
 
In [2]: my_slice_meaning = slice(0,5,2)
 
In [3]: a[my_slice_meaning]
Out[3]: [1, 2, 1]

48 拿来就用的排序函数

排序：

In [1]: a = [1,4,2,3,1]
 
In [2]: sorted(a,reverse=True)
Out[2]: [4, 3, 2, 1, 1]
 
In [3]: a = [{'name':'xiaoming','age':18,'gender':'male'},{'name':'
     ...: xiaohong','age':20,'gender':'female'}]
In [4]: sorted(a,key=lambda x: x['age'],reverse=False)
Out[4]:
[{'name': 'xiaoming', 'age': 18, 'gender': 'male'},
 {'name': 'xiaohong', 'age': 20, 'gender': 'female'}]

49 求和函数

求和：

In [181]: a = [1,4,2,3,1]
 
In [182]: sum(a)
Out[182]: 11
 
In [185]: sum(a,10) #求和的初始值为10
Out[185]: 21

50 转元组

tuple() 将对象转为一个不可变的序列类型

In [16]: i_am_list = [1,3,5]
In [17]: i_am_tuple = tuple(i_am_list)
In [18]: i_am_tuple
Out[18]: (1, 3, 5)

51 查看对象类型

class type(name, bases, dict)

传入一个参数时，返回 object 的类型：

In [1]: class Student():
   ...:     def __init__(self,id,name):
   ...:         self.id = id
   ...:         self.name = name
   ...:     def __repr__(self):
   ...:         return 'id = '+self.id +', name = '+self.name
   ...: 
   ...: 
 
In [2]: xiaoming = Student(id='001',name='xiaoming')
In [3]: type(xiaoming)
Out[3]: __main__.Student
 
In [4]: type(tuple())
Out[4]: tuple

52 聚合迭代器

创建一个聚合了来自每个可迭代对象中的元素的迭代器：

In [1]: x = [3,2,1]
In [2]: y = [4,5,6]
In [3]: list(zip(y,x))
Out[3]: [(4, 3), (5, 2), (6, 1)]
 
In [4]: a = range(5)
In [5]: b = list('abcde')
In [6]: b
Out[6]: ['a', 'b', 'c', 'd', 'e']
In [7]: [str(y) + str(x) for x,y in zip(a,b)]
Out[7]: ['a0', 'b1', 'c2', 'd3', 'e4']