Python Basic Grammar Compilation Summary

Find Help document Dir (method) helper (method)

For example: Dir (list) to find out the various methods of the list

The python variable is equivalent to a label, which is affixed to that big, which is where to hit

Input: A=int (Input (' Please enter an integer: '))

Output: Print (' The value of this integer is ', a)

Python does not have a function or loop of bounding brackets, only according to indentation to identify that the code is within the loop (that is, those code is the loop body),

Conditional statements are added after the if else or while statement: that is, a colon

Python variables are not defined, used directly, but more visually, a label.

Indentation is important and does not hang else, the same indentation level is the binding

For loops, unlike C, Python's for loop can automatically invoke the iterator's next method and automatically end the loop. Very smart

For-Target in expression:

Loop body

List is an array of C languages

scheduled for number=[1,2,3,4,5,5]

Len () to find the length

Range () and for loop are a pair

Range (1:5) generates 1 to 4 sequence range (5) to generate 0 to 4 sequences

List is an array of C languages

number=[1,2,3,4,5,5] List of everything can be put, the same list of different types of data can also put num=[' 123 ', 123,4] string integer object can be thrown into the list

num=[] Empty list

To add an element to a list:

Append method Num.append (' Zhang ') passed in the string ' Zhang ' but only one element at a time

Extend num.extend ([' Zhang ', ' Li ']) can be expanded as a list to add multiple

Insert (the position in the list, the inserted element)

To insert an element into the list:

Remove (the element to remove) does not need to know where the element to delete exists

Del Delete entire list

The Pop () method takes the last element out and returns the deleted element

Pop (index value) deletes the element corresponding to the index value

Get multiple list elements at once: list shards or slices

Num[1:3] Gets the index value from 1 to 2 elements to get the original list of copies, the original list does not change Num[:3] Gets the element from the first starting position (index 0) to index 2

Num[2:] Gets the index value from 2 to the last element

num[:] All elements

Other operations:

In num if 10 returns 1 in num otherwise returns 0

No in num if 10 does not return 1 in num otherwise returns 0

Num*3 copies elements from the NUM list into three batches if num=[1,2,3] num*3 is

[1,2,3,1,2,3,1,2,3] At this time the * becomes a repeating operator

Num.count (123) finds the number of occurrences of 123 elements in Num and returns

Num.index (123) returns the position of element 123 in the list (default is the first occurrence of the element)

Num.index (123,3,7) find 123 from three to 7

Num. Reverse () The entire list element is reversed in situ

Num.sort () Sort by default small to large sort num.sort (reverse=true) from large to small arrangement

Print (' This is%.4f '%2.12345)

This is 2.1235 format output

Yongzu elements cannot be changed after they are defined, they cannot be deleted and inserted, but the meta-ancestor can be updated this is not the same as the list.

Ganso with parentheses when creating

tuple1= (1,2,3,,4,5,6,7,8) Ganso Tuple1 methods and lists for accessing elements

The definition of the Ganso of an element tuple1= (1,) or tuple=1, must have a comma or the integer type.

Tupl1=1,

Tuple2= (' Zhang ', ' Li ', ' Wang ') updated the Yuan Zu

How to insert an element in Yongzu

tuple1= (' Li Ning ', ' Adidas ', ' Nike ', ' Anta ')

Join 361

tuple1=tuple1[:2]+ (' 361 ',) +tuple2[2:] Stitching

Synthetic Li ning Adidas 361 Nike Anta

String: str

Str= ' I love my school '

STR[2] Find the element with index 2, which is L

Python does not have the concept of a character

str=str[:2]+ (' 361 ',) +str[2:] Some basic operation strings of the concatenation list can also be used with slices, comparison operators, and the logical operator member operator in is not the same as the list

String formatting: The Format function receives positional parameters and keyword arguments

Unknown parameter ' {0} ' love {1}. {2} '. Format (' I ', ' I ', ' now ') curly braces are required to represent substitution fields

' I love You.now '

Keyword parameter ' {a} love {b}. {c} '. Format (a= ' i ', b= ' you ', c= ' now ')

As a result

' {{0} '. Format (' You're awesome ') output ' {0} ' does not output you really good, because 0 has been included in curly braces, lost the meaning of the previous

Formatting:

' {0:.2f}{1} '. Format (2.345, ' result ') where the {0:.2f} colon represents the beginning of the format followed by the formatting operator. Point 2 means keep two decimal places F is floating point number

Formatted strings are the same as printf C language Features

'%c '% 97 played ' a '

Print ('%c '%97)

Formatted integer: Print ('%d '%9.7) output 9

List meta-progenitor strings are indexed and are indexed from 0 can be shards can have some basic operators

Sequence: A generic term for a list of meta-progenitor strings

Common built-in methods for sequences:

List () converts an object into a list object

B= ' I love my school '

B=list (b)

b=[' i ', ' ', ' l ', ' o ', ' V ', ' e ', ' ', ' m ', ' y ', ', ' s ', ' C ', ' H ', ' o ', ' o ', ' l ']

Tuple () Converts an iterative object into a Ganso

Len (a) returns the length of a

Max (a) returns the parameter a (the maximum value of the sequence or the progenitor)

Min (a) returns the parameter a (the minimum value of the sequence or progenitor)

Sum (a) returns and the above four require elements to be unified in order to

Sorted () sort

Reversed () Reverses its result not the inverted ganso but one = an iterator we use:

A Tuple (reversed ()) or list (reversed ()) returns the inverted element

Well

List (Enumerate (a)) enumeration type A is a list enumerate (a) returns an iterator that needs to be added to list to display

[(0, 1), (1, 2), (2, 1), (3, 3), (4, 4), (5, 12)]

Dictionary:

The dictionary defines the dictionary not as a sequence type, but as a mapping type and cannot be accessed with an index.

dir1={' Li Ning ': ' Everything is possible ', ' Nike ': ' Imposible is nothing ', ' anta ': ' Never Stop ',}

Li Ning is key everything can be value values they are separated by a colon

Index:

Print (' Anta slogan is: ', dir1[' Anta ')

Anta's slogan is: Never stop

Example: dir2={1: ' Zhang ', 2: ' Rui ', 3: ' Lin '}

>>> Dir2

{1: ' Zhang ', 2: ' Rui ', 3: ' Lin '}

Create dictionary: dirct1={};

Using the Dict function dict is only one parameter

Dirt3=dict ((1, ' Zhang '), (2, ' Rui '), (3, ' Lin ')) so to disguise the three progenitor as a meta-ancestor that is three parentheses (carefully understood)

>>> Dirt3

{1: ' Zhang ', 2: ' Rui ', 3: ' Lin '}

Modify the dictionary element originally: {1: ' Zhang ', 2: ' Rui ', 3: ' Lin '}

dirt3[1]= ' Dashibi '

>>> Dirt3

{1: ' Dashibi ', 2: ' Rui ', 3: ' Lin '} even if there is no such index in the dictionary, one is added automatically.

Fromkeys Create a new key value and return Note: Only definitions cannot be used to modify elements in the dictionary

Dict5=dict5.fromkeys ((), (' One ', ' one ', ' one ', ' three ')

Output:

{1: (' One ', ' one ', ' ' Three '), 2: (' One ', ' one ', ' three '), 3: (' One ', ' one ', ' three ')}

Dict5=dict5.fromkeys (1, (' One ', ' Zhang ') thought that modifying the first element in the dictionary was actually not,

The output dict5 is 1:zhang and becomes a new dictionary.

E=dict5.fromkeys (Range (12), ' Diao ')

>>> E

{0: ' Diao ', 1: ' Diao ', 2: ' Diao ', 3: ' Diao ', 4: ' Diao ', 5: ' Diao ', 6: ' Diao ', 7: ' Diao ', 8: ' Diao ', 9: ' Diao ', 10: ' Diao ', 11: ' Diao '}

Keys () Usage

>>> for I in E.keys ():

Print (i)

0

1

2

3

4

5

6

7

8

9

10

11

>>>

VALUES () Usage

>>> for I in E.values ():

Print (i)

Mouth

Mouth

Mouth

Mouth

Mouth

Mouth

Mouth

Mouth

Mouth

Mouth

Mouth

Mouth

>>>

Get element

Get () method

Check whether the index value has

For example, check the key value 32

Direct-in E has a return true no return false

In is not a membership operator

Empty dictionary

Clear ()

Pop () The given key pops a value

Popitem () pops up an item

SetDefault (5, ' Baba ') joins a key value of 5 with a value of Baba

Update () updates the dictionary with a mapping relationship

Dirt3={1: ' Zhang ', 2: ' Rui ', 3: ' Lin '}

>>> Dirt3

{1: ' Zhang ', 2: ' Rui ', 3: ' Lin '}

>>> Dirt3.pop (1)

' Zhang '

>>> Dirt3

{2: ' Rui ', 3: ' Lin '}

>>> Dirt3

{2: ' Rui ', 3: ' Lin '}

>>> Dirt3.setdefault (6, ' Baba ')

' Baba '

>>> Dirt3

{2: ' Rui ', 3: ' Lin ', 6: ' Baba '}

>>> b={' Little white ': ' Gou '}

>>> Dirt3.update (b)

>>> Dirt3

{2: ' Rui ', 3: ' Lin ', ' Little white ': ' Gou ', 6: ' Baba '}

Collection:

And the dictionary is cousin

>>> jihe={12,3,4} also use curly braces

>>> type (JIHE)

<class ' Set ' > It's a set that's like a dictionary definition.

The element of the collection is the only duplicate element that will be automatically rejected

The collection is unordered and cannot be indexed

Create collection: jihe={1,2,3,,4}

Set () factory function

Jihe=set ([1,2,3,4]) The parameter of the set () function is now a list, or it can be a ganso or a string

>>> Jihe

{1, 2, 3, 4}

You can use a for loop to read every element

Can be used to determine whether an element is in the collection

Add (1) add element 1

Remove (1) Remove element 1

File operations

F=open (' e:\\recovery.txt ', ' RT ') Open the E-disk under the recovery file read-only mode F for the file object

F.read () Read all

' Rui UI Anhui people room card charge way to tell \ Haverdahl start a holiday achilles \ \ Love the plane Dragonair master fell in love with coffee \nafsjkfnalkf, \ n Love began to send greeting cards called Master good \ n '

The read pointer at this point points to the last

>>> f=open (' e:\\recovery.txt ', ' RT ')

>>> F.read (4) read five character (s)

' Rui UI '

>>> F.tell () read out where the pointer is

7

Python is flexible.

Can convert a file object into a list

>>> f=open (' e:\\recovery.txt ', ' RT ')

>>> list (f)

[' Rui UI Anhui people room card charge way to tell \ n ', ' Haverdahl began to holiday Achilles \ \ ', ' fell in love with the plane Dragonair master love coffee \ n ', ' afsjkfnalkf, \ n ', ' love began to send greeting cards called Master Good '] that content is included in the

Every line is read out.

>>> f=open (' e:\\recovery.txt ', ' RT ')

>>> a=list (f)

>>> for I in a:

Print (i)

Rui UI Anhui people room card charge way tell

Haverdahl started a holiday, Achilles.

Fell in love with the plane Dragonair master was in love with coffee

AFSJKFNALKF,

Love begins to send a greeting card called Master good

Write file:

>>> file=open (' E:\\test.txt ', ' W ')

>>> file.write (' Zhangruilin ') write Zhangruilin

11

>>> File.seek (0,0) pointer zeroing

0

>>> for i in file: output

Print (i)

Module:

Some operations on files in the OS module

Import OS Importing module

OS.GETCWD ()

Os.listdir (' e:\\ ')

Os.mkdir (' c:\\b ')

>>> os.remove (' d:\\ from. jpg ')

>>> os.rmdir (' c:\\b ')

Os.path modules are useful

Pickle Module

Can be used to save files, saved as various types of files, not limited to text files

Convert complex data types, such as list dictionaries, into binary files.

>>> m_list=[123,3.14, ' Zhangruilin ', [' answer ']

>>> pickl_file=open (' my_list.pkl ', ' WB ') suffix does not matter the content is not changed WB read-only binary save step

>>> pickle.dump (m_list,pickl_file) Save file

>>> Pickl_file.close ()

>>> pickl_file=open (' my_list.pkl ', ' RB ')

>>> my_list=pickle.load (Pickl_file) reply to the entire list read out step

>>> my_list

[123, 3.14, ' Zhangruilin ', [' answer ']

Example: Save some unnecessary files through the Pickle module

>>> m_list1=[' 123 ', ' 234 ']

>>> pickle1=open (' c:\\zhangruilin.pkl ', ' WB ')

>>> pickle1=open (' c:\\zhangruilin.pkl ', ' WB ')

>>> Pickle.dump (M_list1,pickle1)

>>> Pickle1.close ()

>>> pickle1=open (' c:\\zhangruilin.pkl ', ' RB ')

>>> A=pickle.load (Pickle1)

>>> A

[' 123 ', ' 234 ']

Abnormal:

Try:

F=open (' C:\\ac.txt ', ' W ')

Print (F.write (' I exist '))

sum=1+ ' 1 '

F.close ()

Except (Oserror,typeerror):

Print (' ERROR ')

Finally

F.close ()

Rich Else statement else can match while and try

Executes the next else statement when it is not executed in the while

The Else statement is executed when there is no error in the try

Try:

F=open (' C:\\ac.txt ', ' W ')

Print (F.write (' I exist '))

sum=1+ ' 1 '

F.close ()

Except (Oserror,typeerror):

Print (' ERROR ')

Else:

Print (' zhangrui;in ') when there is no error in the try, it executes the

A=1

While a!=2:

Print (' Nishishiba ')

a++

Else: Executes the else statement when the while does not execute

Print (' Sadiyage ')

The WITH statement abstracts out some common actions of the file, helping us to automatically close the file

Try:

With open (' C:\\ac.txt ', ' W ') as F:with will pay attention to when this file is not used he will automatically call off

Print (F.write (' I exist '))

sum=1+ ' 1 '

Except (Oserror,typeerror):

Print (' ERROR ')

Start of class capital letters in Puthon, start of function lowercase letter

Python is an object-oriented inheritance package polymorphism has

Inherited

Class A (list): Parameter list means that Class A inherits the list class

Pass represents this class and does nothing just to demonstrate

>>> B=a ()

>>> B.append (34) object B inherits all functions of the list class

>>> b

[34]

Python's self and C + + 's This pointer is the identity symbol (identifying an object) of each class's object

The definition takes care to write self into the first argument when the class is defined.

Class Gun:

def fun (self,name):

Self.name=name

def shoot (self):

Print (' The Weapon function is%s '%self.name)

>>> A=gun ()

>>> A.fun (' Machine gun ')

>>> B=gun ()

>>> B.fun (' Automatic rifle ')

>>> A.shoot ()

The weapon function is machine gun

>>> B.shoot ()

The weapon function is an automatic rifle

Magic Method:

_init_ (SELF,CANSHU1,CANSHU2) function is C + + constructor Note double underline

Class Gun:

def __init__ (self,name):

Self.name=name automatically called when an object is established

def shoot (self):

Print (' The Weapon function is%s '%self.name)

>>> B=gun (' Heavy machine gun ') call without tube first parameter

>>> B.shoot ()

The weapon function is heavy machine gun

Private variables in Python define private variables with two underscores in front of the variable name or function name

Super. Plus the method of the required parent class () Super can help us invoke the method defined by the parent class

For example:

Import Random as R

Class Fish:

def __init__ (self):

Self.x=r.randint (0,10)

Self.y=r.randint (0,10)

def move (self):

Self.x-=1

Print (' My location is: ', SELF.X,SELF.Y)

Class Goldfish (fish):

Pass

Class Salman (fish):

Pass

Class Carp (fish):

Pass

Class shark (fish):

def __init__ (self):

Super (). __init__ () No name given to any base class

Self.hungry=true

Def eat (self):

If Self.hungry:

Print (' The dream of a foodie is to eat every day ')

Self.hungry=false

Else

Print (' Fed up, can't eat ')

>>> Shark=shark ()

>>> Shark.move ()

My position is: 9 1

Python Basic Grammar Compilation Summary