Python Iteration and List Builder

Using a For loop to traverse list and tuple, this traversal becomes an iterative

In the C language is the subscript to get the value, for...in this way is actually the same.

In the section of the function, this says---> ' Sum function sum (), sum (Iterable,start), the first parameter must be an object that can be iterated, listtuple. ' Iterative objects are list,tuple

So when using for traversal, the object is to be iterated.

How do I tell if an object can iterate?

The iterable of Python's collections module can be used to determine whether iterations can be iterated;isinstance()函数用来判断某种数据类型是否是已知的类型

 >>>isinstance (1,int) 
 Ture 
 > >>isinstance (' abc ', str) 
 Ture 
 >>>isinstance (3.14,float) 
 Ture 
 >>>isinstance ( ' 3.14 ', float) 
 False 
 ##################################### 
 
 
 from  collections import  iterable  
 >>>isinstance ([1,2,3,4,5 ],iterable)  
 ture  
 >>> Isinstance (12345,iterable)  
 false  
 >>>isinstance ((1,2,3,4,5), iterable)  
 ture  
 >>>isinstance ({' Name ': ' JKL ', ' age ': 15},iterable)  
 ture  

So dict can use the for traversal key or values or key,values

Dict is an iterative object, depending on the use of the environment

How do I get a list or a tuple to display subscripts and elements at the same time?

Python provides the enumerate () function, which turns the list or tuple into: index-element pairs, like key-value pairs

t = [1,2,3,4,5] for in enumerate (t)        print(k, '-', V)
0-1
1-2
2-3
3-4
4-5
5-6

List-Generated

To generate an L = [2,4,6,8,10,12,14,...... 100] such a list;

Can be sliced out:

#这里使用list () Convert the number of sequences generated by the range () function to List,tuple also in the same way
>>>l = List (range (1,101= l[1::2]>>>l1[2,4,6,8,10,........]

You can also use functions:

DEF create ():
    L = []
    For x in range (1,51):
            L.append (x*2)
    Print (L)
    Return

Create ()
[2,4,6,8,10,12,...... 100]

The above code is very troublesome, the use of a list generated by a row can be resolved

 for  in range (1,101) [2,4,6,8,10,..... 100]

The build can also be nested in two for loops, resulting in a full-array

 for inch  for  in range (1,5) [1,2,3,4,2,4,6,8]

Diego represents the up-type

t = (1,2,3,4,5,6 for in t][1,2,3,4,5,6]

Plus other qualifications: A list contains multiple data types, takes out a string and capitalizes the first letter

L = ['grant','Fitz', 15,3.14for in  If  instance (x,str) ['Grant','Fitz  ']

Python Iteration and List Builder