Python Foundation 3: Basic data types

Basic data Type one, int, shaping A, creation method

N1 = 123

N2 = Int (123)

b, int internal optimization

The default number of -5~257 is shared with one address

= = = ID (object memory address) = ID (object or variable name)

c, Length limit

32-2**31~2**31-1

-2**63~2**63-1

There's no limit in py3.

Second, str, string A, how to create

S1 = "Alex"

S1 = str ("Alex")

B, Unique features

SL = "Alex"

1, both ends go blank: s1.strip

2. To ... Beginning: S1.startswith ()

3, find sub-series "", "H": S1.find ()

4. Replace a subsequence in a string with the specified value: S1.replace ()

5. Capitalization: S1.upper ()

6, is ... : S1.isalphe ()

7. Join what is connected in what form:

Li = ["Alex", ' SB ']

L1 = "_". Join (LI)

L1 the corresponding value ALEX_SB

C, Public function

Index: Only one element can be taken

Slices: Fetching multiple elements

Len: Calculate element length

3.5 is represented by characters.

2.7 Inside is byte

For

3.5 is represented by characters.

　　　　

Encoding, for:
Name = "Lu Li"
For I in Name:
Print (i)
bytes_list = (Bytes (i,encoding= ' utf-8 '))
Print (bytes_list)
For B in Bytes_list:
1, 3.5 for loop, every element of the loop is a "character"

2, character = = "Byte:
bytes_list = Bytes ("string", encoding= "Utf-8")

Utf-8 = "3 bytes
GBF = "2 bytes
Print (bytes_list) #默认每一个字节都是16进制表示
For B in Bytes_list:
Print (b) #默认没一个字节都是10进制表示
　　
3, 10 binary digits = = "2 binary
Len
Id

Bin (plus a 10-digit number, which becomes 2 binary)

　　　　

D, Byte, and string conversions: bytes and str

　　　　　

A ="Lu Li"            #Convert a string to bytesB1 = bytes (a,encoding="Utf-8")            Print(B1) B2= Bytes (a,encoding='GBK')            Print(B2)#Convert bytes to StringsNewal = str (b1,encoding="Utf-8")            Print(Newal) newa2= STR (b2,encoding="GBK")            Print(NEWA2)

list, listing A, how to create

Li = [11,22,33,44]

Li = List ()

Li = List ([11,22,33,44])

B, Conversion

1. Convert strings into lists

" Lu Li " # for, the character ==> can iterate li = List (s1)#forLoop, which will loop through each element as a list of elements #["Li" " Lu"]  Print(li)# result: [' Lee ', ' Lucy ']

2. Tuples converted to lists

# tuples converted to list t2 = ("Acker""seven""  Laolanhai"= list (t2)print(L2)# result: [' Acker ', ' seven ', ' Laolanhai ']

3. Dictionary conversion to List

#dictionaries converted to listsDIC = {"K1":"Alex","K2":"Seven"}l3=list (Dic.items ())Print(L3)#results: [(' K1 ', ' Alex '), (' K2 ', ' Seven ')]#The dictionary consists of key and values#string, tuple, dictionary ==> list

C, Unique features

Li = [111,22,3]

1, Append: Li.append ()

2, clear: Li.clear ()

3, flip, inside the byte element flip: Li.reverse ()

4. Insert the specified element into the specified position: Li.insert (1, "X")

5, go to Space: Li.strip ()

6.

# expands bytes to the inside of a byte with another iterated object # str,list,dic,tupleli = [111,22,3" lu Li "li.extend (s)print  (LI)# results: [111, 22, 3, ' Li ', ' Lulu ']

D. Public functions

Li = ["Alex", "Aric", "Sevev", "123"]

Index: li[2]

Slice: li[2:3]:::*** What kind of the original is what type, the list is also a list of tiles * * *

For

Len

del# Delete

Example of an index nesting: Remove the 2nd "123":

Li = ["Alex", 123, {"K1": "V1", "K2": {"VV": (One, one, 123), "II": 456}}]

LI[2]-->{"K1": "V1", "K2": {"VV": (One, one, 123), "II": 456}}

li[2][' K2 '-->{"VV": (One, one, 123), "II": 456}

li[2][' K2 ' ["VV"]--(11, 22, 123)

li[2][' K2 ' ["VV"][2]-->123

Iv. tuple A, creation and conversion

t = (11,22,33)

t = tuple ((11,22,33))

t = tuple ([]) #字符串, list, dictionary

# tuples are converted to lists t2 = ("Acker","seven","  Laolanhai"= list (t2)print(L2)# result: [' Acker ', ' seven ', ' Laolanhai ']

B. Unique methods

#add content to tuples#tuplet = (11,22,["Alex",{"K1":"v1"}]) t[2][1]['K2'] = 123Print(t)#results: (one, one, [' Alex ', {' K1 ': ' v1 ', ' K2 ': 123}])T[2][1].update ({'K3': 123})Print(t)#results: (one, one, [' Alex ', {' K1 ': ' v1 ', ' K2 ': 123, ' K3 ': 123}])

Count

Index

C, nesting (get Element)

　　　　　

T = (one, one, ["Alex", {"K1", "v1 ")  = t[2][1]["K1"]print(L1)# Results: v1

D, tuples, characteristics:

The son cannot be modified.

E, collation:

Generic string, performs a function, generates a new content, the original content is unchanged list,tuple,dict,

Perform a function that changes itself

V. Dictionary a, creating

A = {"K1": 123}

A = Dict ()

#dictionaries converted to listsDIC = {"K1":"Alex","K2":"Seven"}l3=list (Dic.items ())Print(L3)#results: [(' K1 ', ' Alex '), (' K2 ', ' Seven ')]#The dictionary consists of key and values#string, tuple, dictionary ==> list

b, the use of enumerate

Converts a list to a dictionary {key:10 sliding scale, value: the element in the table}

li = [one, A, dict (enumerate (li,10))#Enumerate can automatically add a column of keys to form the dictionary print (new_dict) # Result: {10:11, 11:22, 12:33}

　　　C, add content in the dictionary:

 #   dictionary add content  dic = {  " k1   ": "  v1   "  " #   Method 1  #   Dic.update ({' K2 ': 123})  #   print (DIC)  #   Method 2  dic[ "  K2   "] = 123print   (DIC)  #   result: {' K1 ': ' v1 ', ' K2 ': 123} 

　　　　

# a handy way to add a dictionary d ={"K1":'v1'}# d.update ({' K2 ': 123})d['K2'] = 123# if replaced by: d[' k1 '] = 123 is the V1 can be updated print(d)# result: {' K1 ': ' v1 ', ' K2 ': 123}

D, the use of Fromkeys

#How to get K1,K2, the default value is AlexDIC = {'K1': 123,'K2': 456,'K4': 111}n= Dic.fromkeys (['K1','K2'],'Alex')Print(n)#result: {' K1 ': ' Alex ', ' K2 ': ' Alex '}

　　　　

　　　　

　　　

　　

　　　　

Python Foundation 3: Basic data types