Python data types-lists, tuples, dictionaries

* List Generation

* Meta-Group

* Dictionary

The following experiments are performed by the 2.7 release

One, List generation

1. Syntax:

Range (Starti stop step) 2.7 version

List (range (Starti stop Step)) 3.5 version

Generate a list of numbers from 1 to 10;

Print (List.pop ()); A=list (range (1,10));p rint (a) # # # [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

2. Generate the list by looping:

Syntax: [x for X in range (Starti,stop)]

The first "X": From the beginning

The second "X": is to the number of the first few

print ([x for X in range (1,11)]); ######[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

3. Using a list derivation to generate an even number greater than 20 within 100

print [x for x in range (0,101) if x% 2==0 and x>20]

[Expr for Iter_var in iterable if COND_EXPR]

Add judgment, only satisfies the condition content, only then puts the iterable in the ITER.

b = Range (1,11)

Print B #[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

c = Range (1,11,2)

Print C #[1, 3, 5, 7, 9]

Two, the meta-group

1. What is a tuple: Also a container type, the elements of a tuple cannot be modified, and tuples use parentheses to wrap the data

2. How to create: add elements in parentheses, separated by commas

tup1= (' Kate ', ' Lisa ', 1997,2000), tup2= (1,2,3,4,5) tup3= ' A ', ' B ', ' C ', ' d ' Print (tup1);p rint (tup2);p rint (TUP3); # # (' Kate ', ' Lisa ', 1997, (1, 2, 3, 4, 5) (' A ', ' B ', ' C ', ' d ')

3. How to create an empty tuple

Tup= ()

When you include only one element in a tuple, you need to add a comma after the element

Tuples are similar to strings, and subscripts start at 0 and can be combined

4. Access to tuples:

Tuples can use subscript to ask the value

tup1= (' Kate ', ' Lisa ', 1997,2000);p rint (Tup1[0:2]); # # (' Kate ', ' Lisa ')

5. Modifying tuples

element values in tuples are not allowed to be modified, but we can concatenate combinations of tuples

eg

tup1= (' abc ', ' Def '); tup2= (' Lisi ', ' Kate '); Tup3=tup1+tup2;print (TUP3); # # (' abc ', ' Def ', ' Lisi ', ' Kate ')

6. Delete a tuple

The elements in the tuple are not allowed to be deleted, and you can delete the entire tuple with the DEL statement

del tuple;//The execution of the statement will be an error

7. Tuple operators

Combine, copy, and create a new tuple after an operation

A.len (): Displays the length of the list

B. Connection +

C. Replication

Print ((a) * # (1, 2, 3, 1, 2, 3)

D. Whether the element exists (the return value is a bool value)

Print (3 in ()); # #True

E. Iteration (looping through tuple elements)

Grammar:

For x in tuples:

Print (x)

eg

list= (' Lisi ', ' Kate ', ' Zhangsan ', ' 1900 '); for x in List:print (x); # #lisikatezhangsan1900

8. Meta-group interception

A= (' How ', ' is ', ' you ')

A[1]

A[-2]

A[1:]//are You

9. No closing separator

x,y=1,2

Print (x, y)//2.7 version

##

(1, 2)

10. Meta-set built-in functions

A.len (t): View list length

B.max (t): Maximum value in list

C.min (t): Minimum value in list

D.tuple (lists) convert a list to a tuple

Third, the dictionary

A dictionary is also known as an associative array (hash list), which consists of keys and values, paired objects.

Object = Data + method

1. Dictionary Features:

①. Unordered (element access via key)

②. Variable: Change the value by key

eg

x={' ename ': ' Lisi ', ' SX ': +, ' yw ': +, ' yy ': 60}x[' ename ']= ' Kate ' Print (x); ###{' yy ': $, ' ename ': ' Kate ', ' sx ': ' yw ': 90}

③. Heterogeneous: Supports multiple data types

④. Nesting: dictionaries, lists, tuples can appear in the values section of a key-value pair

x={' ename ': ' Lisi ', ' SX ': ' x ', ' yw ': ' yy ':(2,3 '}x[' ename ']= ' Kate ' print (×); ###{' yy ': (2, 3), ' ename ': ' Kate ', ' SX ': 100 , ' yw ': 90}

If the same key appears two times at a time, the latter value is remembered

2. Dictionary definitions:

Method One: {key1:value1,key2:value2 ... }key1 must be wrapped in quotation marks

Note: Keys in the dictionary must be unique, and values may not be unique

Method Two: Dict () built-in function, specify the health value

X=dict (ename= ' fbb ', sx=95,yw=65)

The value in the dictionary: x[' ename ']

X=dict (ename= ' fbb ', sx=95,yw=65);p rint (x[' ename '); # # #fbb

3. Modify the values in the dictionary:

Syntax: X[key]=value

Add new element: X[newkey]=newvalue

X={' A ': 1, ' B ': 2, ' C ': 3};x[' C ']=5;print (x); ###{' A ': 1, ' C ': 5, ' B ': 2}

4. Delete dictionary elements (x dictionary)

1 removing elements from a dictionary

Del x[' key ']

2. Clear all the entries in the dictionary

X.clear ()

3. Delete the entire dictionary

Del x (x is the dictionary name)

5. Variable unpacking: items () Convert dictionary to key, value as a list of tuples

Syntax: X.items ()

eg

X={' A ': 1, ' B ': 2, ' C ': 3};p rint (X.items ()); ###[(' A ', 1), (' C ', 3), (' B ', 2)]

Fetch key only: keys ()

X.keys ()

X={' A ': 1, ' B ': 2, ' C ': 3};p rint (X.keys ()); ###[' A ', ' C ', ' B ']

Value only: VALUES ()

X.values ()

X={' A ': 1, ' B ': 2, ' C ': 3};p rint (X.values ()); ###[1, 3, 2]

Has_key (): Determines whether a key exists, the return knot is a bool value

X.has_key (' key ')

eg

X={' A ': 1, ' B ': 2, ' C ': 3};p rint (X.has_key (' a ')); # # #True

Len (): Gets the number of key-value pairs in the dictionary

Len (x)

eg

X={' A ': 1, ' B ': 2, ' C ': 3};p rint (len (x)); # # #3

Update (): Merges the dictionary on the original dictionary, overwriting the same key

Syntax: X1.update (x2);

X1={' A ': 1, ' B ': 2, ' C ': 3};x2={' a ': 3, ' d ': 4, ' E ': 5};x1.update (x2);p rint (x1); ####{' A ': 3, ' C ': 3, ' B ': 2, ' E ': 5, ' d ': 4}

This article from the "Breeze with You" blog, declined reprint!

Python data types-lists, tuples, dictionaries