1 Find the absolute value
absolute value or modulo of a complex number
In [1]: abs(-6)Out[1]: 6
2 elements are both true
Accepts an iterator, 所有元素returns if all of the iterators are true, Trueotherwise returnsFalse
In [2]: all([1,0,3,6])Out[2]: FalseIn [3]: all([1,2,3])Out[3]: True
3 elements at least one is true
Accepts an iterator, 至少有一个returns if the element in the iterator is true, Trueotherwise returnsFalse
In [4]: any([0,0,0,[]])Out[4]: FalseIn [5]: any([0,0,1])Out[5]: True
4 ascii display objects
Call the __repr__() method of the object to obtain the return value of the method. The return value of the following example is a string
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 = xiaomingIn [4]: ascii(xiaoming)Out[4]: 'id = 001, name = xiaoming
5 ten to two
will 十进制convert to二进制
In [1]: bin(10)Out[1]: '0b1010'
6 ten to eight
will 十进制convert to八进制
In [1]: oct(9)Out[1]: '0o11'
7 ten to sixteen
will 十进制convert to十六进制
In [1]: hex(15) Out[1]: '0xf'
Judgment is true or false
Tests whether an object is True or False.
In [1]: bool([0,0,0])Out[1]: TrueIn [2]: bool([])Out[2]: FalseIn [3]: bool([1,0,1])Out[3]: True
9 String to byte
converts one 字符串into 字节the type
In [1]: s = "apple"In [2]: bytes(s,encoding='utf-8')Out[2]: b'apple'
10 converted to string
Convert 字符类型, , 数值类型etc. to 字符串types
In [1]: i = 100In [2]: str(i)Out[2]: '100'
11. Is it callable
Determine whether the object can be called. The object that can be called is an callable object, such as a function str, int etc., which can be called, but xiaomingthe instance in Example 4 cannot be called:
In [1]: callable(str)Out[1]: TrueIn [2]: callable(int)Out[2]: TrueIn [3]: xiaomingOut[3]: id = 001, name = xiaomingIn [4]: callable(xiaoming)Out[4]: False
If you want xiaomingto be able to call xiaoming(), you need to override the method Studentof the class __call__:
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 calledmy name is xiaoming
12 ten turn ASCII
View the corresponding decimal integerASCII字符
In [1]: chr(65)Out[1]: 'A'
13 ASCII turn ten
View a ASCII字符corresponding decimal number
In [1]: ord('A')Out[1]: 65
14 Static methods
classmethod The function corresponding to the decorator does not need to be instantiated and does not need selfparameters, but the first parameter needs to be the cls parameter representing its own class, which can be used to call the properties of the class, the method of the class, the instantiated object, etc.
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 Execute the code represented by the string
Compile the string into code that python can recognize or execute, or read the text into a string and then compile it.
In [1]: s = "print('helloworld')"In [2]: r = compile(s,"<string>", "exec")In [3]: rOut[3]: <code object <module> at 0x0000000005DE75D0, file "<string>", line 1>In [4]: exec(r)helloworld
16 Create complex numbers
create a plural
In [1]: complex(1,2)Out[1]: (1+2j)
17 Dynamically delete attributes
delete object properties
In [1]: delattr(xiaoming,'id')In [2]: hasattr(xiaoming,'id')Out[2]: False
18. Convert to dictionary
Create data dictionary
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 View all methods of an object with one click
当前范围Returns a list of variables, methods, and defined types when there are no parameters ; returns 参数a list of attributes and methods when there are parameters.
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 Take quotient and remainder
Take the quotient and remainder separately
In [1]: divmod(10,3)Out[1]: (3, 1)
21 enumeration objects
Returns an enumerable object whose next() method will return a tuple.
In [1]: s = ["a","b","c"]...: for i ,v in enumerate(s,1):...: print(i,v)...:1 a2 b3 c
22 Calculation expressions
Evaluate the string str as a valid expression and return the calculation result to extract the contents of the string
In [1]: s = "1 + 3 +5"...: eval(s)...:Out[1]: 9
23.View the number of bytes occupied by variables
In [1]: import sysIn [2]: a = {'a':1,'b':2.0}In [3]: sys.getsizeof(a) # 占用240个字节Out[3]: 240
24 filters
Set the filter condition in the function, iterate the elements, and keep Truethe element whose return value is:
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.Convert to floating point type
Converts an integer or numeric string to a floating point number
In [1]: float(3)Out[1]: 3.0
If it cannot be converted into a floating point number, it will report 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 String Formatting
To format the output string, format(value, format_spec) essentially calls the __format__(format_spec) method of value.
In [104]: print("i am {0},age{1}".format("tom",18))i am tom,age18
| 3.1415926 | {：.2f} | 3.14 | Keep two decimal places |
| 3.1415926 | {：+2f} | +3.14 | Signed to two decimal places |
| -1 | {：+2f} | -1.00 | Signed to two decimal places |
| 2.71828 | {:.0f} | 3 | without decimals |
| 5 | {:0>2d} | 05 | Numeric zero padding (padding to the left, width is 2) |
| 5 | {:x<4d} | 5xxx | Number complement x (fill right, width is 4) |
| 10 | {:x<4d} | 10xx | Number complement x (fill right, width is 4) |
| 1000000 | {:,} | 1,000,000 | comma-separated number format |
| 0.25 | {:.2%} | 25.00% | percentage form |
| 1000000000 | {:.2e} | 1.00e+09 | Exponential notation |
| 18 | {:>10d} | ‘18’ | Align right (default, width 10) |
| 18 | {：＜10d} | ‘18’ | Align left (width 10) |
| 18 | {：^10d} |
‘18’ | Center aligned (width 10) |
27 Freeze Collection
Create an unmodifiable collection.
In [1]: frozenset([1,1,3,2,3])Out[1]: frozenset({1, 2, 3})
Since it is not modifiable, there is no sum method like setthataddpop
28 Get object properties dynamically
Get the properties of the object
In [1]: class Student():...: def __init__(self,id,name):...: self.id = id...: self.name = name...: def __repr__(self):...: return 'id = '+self.id +', name = '+self.nameIn [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 Does the object have this attribute
In [1]: class Student():...: def __init__(self,id,name):...: self.id = id...: self.name = name...: def __repr__(self):...: return 'id = '+self.id +', name = '+self.nameIn [2]: xiaoming = Student(id='001',name='xiaoming')In [3]: hasattr(xiaoming,'name')Out[3]: TrueIn [4]: hasattr(xiaoming,'address')
30 returns the hash value of the object
Returns the hash value of the object. It is worth noting that custom instances are all hashable, and variable objects such as , list, dictand setso on are all unhashable (unhashable)
In [1]: hash(xiaoming)Out[1]: 6139638In [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'