Hi, I’m Chi Ye
Today, I’m going to show you some basic python examples to help you remember. Here are 52 examples
1 finding absolute value
Magnitude of absolute value or complex number
In [1]: abs(-6)
Out[1]: 6
Copy the codeThe two elements are all true
Accepts an iterator that returns True if all elements of the iterator are True, False otherwise
In [2] : all (,0,3,6 [1]) Out [2] : False In [3] : all ([1, 2, 3]) Out [3] : TrueCopy the codeAt least one of the 3 elements is true
Accepts an iterator, returning True if at least one element in the iterator is True, False otherwise
In [4] : any ([0, 0, []]) Out [4] : False In [5] : any ([0, 1]) Out [5] : TrueCopy the code4 ASCII Display object
Call the __repr__() method of the object and get the return value of the method, which is a string in the following example
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'Copy the code5十 turn 2
Convert decimal to binary
In [1]: bin(10)
Out[1]: '0b1010'
Copy the codePatriarch turned eight
Convert decimal to octal
In [1]: oct(9)
Out[1]: '0o11'
Copy the codeSeven ten to sixteen
Convert decimal to hexadecimal
In [1]: hex(15)
Out[1]: '0xf'
Copy the code8 Determine whether it is true or false
Tests whether an object is True or False.
In [1] : bool (0, 0) Out [1] : True In [2] : bool ([]) Out [2] : False In [3] : bool ([1, 1]) Out [3] : TrueCopy the code9 String to bytes
Converts a string to a byte type
In [1]: s = "apple"
In [2]: bytes(s,encoding='utf-8')
Out[2]: b'apple'
Copy the code10 Converting to a String
Converts character types, numeric types, and so on to string types
In [1]: i = 100
In [2]: str(i)
Out[2]: '100'
Copy the code11 Check whether it can be called
Callable (STR, int, etc.); example 4: Xiaoming is not callable.
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
Copy the codeIf you want xiaoming() to be called, you need to override Student’s __call__ method:
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 xiaomingCopy the code120 turn ASCII
View the ASCII characters of a decimal integer
In [1]: chr(65)
Out[1]: 'A'
Copy the code13 turn ten ASCII
View the decimal number of an ASCII character
In [1]: ord('A')
Out[1]: 65
Copy the code14 Static Methods
The function corresponding to the classMethod decorator does not need to be instantiated, does not need to take the self argument, but the first argument needs to be the CLS argument representing its own class, can call the class properties, class methods, instantiated objects, 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)Copy the code15 Executes the code represented by a string
Compile the string into code that Python recognizes or can execute, or read the text as a string and then compile it.
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
Copy the code16 Creating complex Numbers
Create a complex number
In [1]: complex(1,2)
Out[1]: (1+2j)
Copy the code17 Dynamically delete attributes
Deletes an attribute of an object
In [1]: delattr(xiaoming,'id')
In [2]: hasattr(xiaoming,'id')
Out[2]: False
Copy the code18 Turn into a dictionary
Creating a 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} [4] : In dict ([(' a ', 1), (" b ", 2)]) Out [4] : {' a ', 1, 'b' : 2}Copy the code19 View all object methods in one click
Returns a list of variables, methods, and types defined in the current range without arguments; Returns a list of properties and methods for an argument.
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']
Copy the code20 quotient and remainder
Take the quotient and remainder
In [1]: divmod(10,3)
Out[1]: (3, 1)
Copy the code21 Enumeration Object
Returns an enumerable object whose next() method returns a tuple.
In [1]: s = ["a","b","c"] ... : for i ,v in enumerate(s,1): ... : print(i,v) ... : 1 a 2 b 3 cCopy the code22 Calculation expression
Evaluates the string STR as a valid expression and returns the result to fetch the contents of the string
In [1]: s = "1 + 3 +5" ... : eval(s) ... : Out[1]: 9Copy the code23 Check the number of bytes in the variable
In [1]: import sys In [2]: a = {'a':1,'b':2.0} In [3]: sys. getSizeof (a) # Out[3]: 240Copy the code24 filter
Set the filter condition in the function, iterating over the elements, keeping the elements that return True:
In [1] : fil = filter (lambda x: x > 10,,11,2,45,7,6,13 [1]) In [2] : list (fil) Out [2], [13] 11, 45,Copy the code25 Convert to a floating point type
Converts an integer or numeric string to a floating point number
In [1]: float(3)
Out[1]: 3.0
Copy the codeIf it cannot be converted to a floating point number, ValueError is raised:
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'Copy the code26 String Formatting
Format (value, format_spec) essentially calls the __format__(format_spec) method of value to format the output string.
In [104]: print("i am {0},age{1}".format("tom",18))
i am tom,age18
Copy the code| 3.1415926 | {:.2f} | 3.14 | Keep two decimal places |
|---|---|---|---|
| 3.1415926 | {:+.2f} | + 3.14 | The sign preserves two decimal places |
| – 1 | {:+.2f} | 1.00 | The sign preserves two decimal places |
| 2.71828 | {:.0f} | 3 | With no decimal |
| 5 | {:0>2d} | 05 | Numeric zeroing (padding left, width 2) |
| 5 | {:x<4d} | 5xxx | Number fill x (fill right side, width 4) |
| 10 | {:x<4d} | 10xx | Number fill x (fill right side, width 4) |
| 1000000 | {:} | 1000000 | Number format separated by commas |
| 0.25 | } {: 2% | 25.00% | Percentage format |
| 1000000000 | {:.2e} | 1.00 e+09 | Index notation |
| 18 | {:>10d} | ’18’ | Right aligned (default, width 10) |
| 18 | {:<10d} | ’18’ | Left aligned (width 10) |
| 18 | {:^10d} | ’18’ | Middle alignment (width 10) |
27 Frozen Set
Create a collection that cannot be modified.
In [1] : frozenset (,1,3,2,3 [1]) Out [1] : frozenset ({1, 2, 3})Copy the codeBecause they cannot be modified, there are no add and pop methods like set
28 Dynamically obtain object attributes
Gets 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.name In [2]: xiaoming = Student(id='001',name='xiaoming') In [3]: Out[3]: 'xiaoming' getattr(xiaoming,'name') #Copy the code29 Check whether the object has 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.name In [2]: xiaoming = Student(id='001',name='xiaoming') In [3]: hasattr(xiaoming,'name') Out[3]: True In [4]: hasattr(xiaoming,'address')Copy the code30 Returns the hash value of the object
Return the hash value of an object. Note that custom instances are hashable. Mutable objects such as lists, dict, and sets are 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'Copy the code31 One-click Help
Returns the help document for the object
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)
Copy the code32 Object door number
Returns the memory address of the object
In [1]: id(xiaoming)
Out[1]: 98234208
Copy the code33 Obtain user input
Gets user input
In [1]: input()
aa
Out[1]: 'aa'
Copy the code34 is an integer
Int (x, base =10), x may be a string or number, converting x to a plain integer. If the argument is a string, it may contain symbols and decimal points. If the range of representations for ordinary integers is exceeded, a long integer is returned.
In [1]: int('12',16)
Out[1]: 18
Copy the code35 isinstance
Returns true if object is an instance of class ClassInfo
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]: TrueCopy the codeIdentification of paternity
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]: TrueCopy the codeTrue is also returned if class is a subclass of an element in the ClassInfo tuple
In [1]: issubclass(int,(int,float))
Out[1]: True
Copy the code37 Create an iterator type
Using iter(obj, sentinel), returns an iterable, sentinel can be omitted (terminates immediately once iterated to this element)
In [1] : LST =,3,5 [1] In [2] : for I the In iter (LST) :... : print(i) ... : 1 3 5Copy the codeIn [1]: class TestIter(object): ... : def __init__(self): ... : the self l =,3,2,3,4,5 [1]... : self.i=iter(self.l) ... : def __call__ (self) : # define the instance of a class of __call__ method is callable... : item = next(self.i) ... : print ("__call__ is called,fowhich would return",item) ... : return item ... : def __iter__ (self) : # support iterative agreement (that is, the definition has __iter__ () function)... : print ("__iter__ is called!!" )... : return iter(self.l) In [2]: t = TestIter() In [3]: __call__ is called,which would return 1 Out[3]: 1 In [4]: for e In TestIter(): Because __iter__ is implemented, t can be iterated over... : print(e) ... : __iter__ is called!! One, three, two, three, four, fiveCopy the code38 Root of all objects
Object is the base class of all classes
In [1]: o = object()
In [2]: type(o)
Out[2]: object
Copy the code39 Opening the File
Return file object
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.'
Copy the codeMode value table:
| character | meaning |
|---|---|
'r' |
Read (default) |
'w' |
Write, and truncate the file first |
'x' |
Exclusive creation fails if the file already exists |
'a' |
Write, appended to the end if the file exists |
'b' |
Binary mode |
't' |
Text mode (default) |
'+' |
Open for update (read and write) |
40 times the power
Base e to the power, mod if given
In [1]: pow(3, 2, 4)
Out[1]: 1
Copy the code41 print
In [5] : LST =,3,5 [1] 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]Copy the code42 Two ways to create attributes
Returns the property property. Typical usage:
class C: def __init__(self): self._x = None def getx(self): return self._x def setx(self, value): self._x = value def delx(self): X = property(getx, setx, delx, "I'm the 'x' property.")Copy the codeUse the Python decorator to achieve exactly the same effect as above:
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
Copy the code43 Create a range sequence
- range(stop)
- range(start, stop[,step])
Generate an immutable sequence:
In [1]: range(11) Out[1]: range(0,11) In [2]: range(0,11,1) Out[2]: range(0,11) Out[2]: range(0,11)Copy the code44 Reverse iterator
In [1] : rev = reversed (,4,2,3,1 [1]) In [2] : for I In rev:... : print(i) ... : 1 3 2 4 1Copy the code45 rounded
Rounding, ndigits indicates the number of digits to keep after the decimal point:
In [11]: round(10.0222222, 3)
Out[11]: 10.022
In [12]: round(10.05,1)
Out[12]: 10.1
Copy the code46 Change to the set type
Returns a set object in which no duplicate elements are allowed:
In [159] : a =,4,2,3,1 [1] In [160] : set Out (a) [160] : {1, 2, 3, 4}Copy the code47 Convert the object into a slice
class slice(start, stop[, step])
Returns a slice object representing the set of indexes specified by range(start, stop, step), which makes the code readable and maintainable.
In [1] : a =,4,2,3,1 [1] [2] : In my_slice_meaning = slice (0,5,2) In [3], a [my_slice_meaning] Out [3] : [1, 2, 1]Copy the code48 just use the sorting function
Sorting:
In [1] : a =,4,2,3,1 [1] [2] : In sorted Out (a, reverse = True) [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'}]Copy the code49 Summing function
Sum:
In [181]: a = [1,4,2,3,1] In [182]: sum(a) Out[182]: 11 In [185]: sum(a,10) # = 10 Out[185]: 21Copy the code50 yuan group
Tuple () converts an object to an immutable sequence type
In [16] : i_am_list =,3,5 [1] In [17] : i_am_tuple = the tuple (i_am_list) In [18] : i_am_tuple Out [18] : (1, 3, 5)Copy the code51 Check the object type
class type(name, bases, dict)
When passed a parameter, return the type of 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.name ... :... : In [2]: xiaoming = Student(id='001',name='xiaoming') In [3]: type(xiaoming) Out[3]: __main__.Student In [4]: type(tuple()) Out[4]: tupleCopy the code52 Aggregate iterator
Create an iterator that aggregates elements from each iterable:
In [1] : x = (3, 2, 1] In [2] : y = (4 and 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']Copy the codeThat’s the end of my sharing, and I hope you found it helpful
Thank you for your support!