python iterate over list

: [expression for x in iterator], [expression for X-in iterator if condition], [expression for X-in iterator for Y-in iterator] ...Note: An expression can be a variable, a constant, a string, a list, a ganso, a dictionary ...Iterate string1>>> s ='ABCDE'2>>> [x forXinchS]3['a','b','C','D','e']4>>>Iterative dictionaries>>> dic = {'name':'Root',' Age': 20,'Gender':'Mans'}>>> [['%s:%s'% (K,V)] forKvinchDic.ite

The Python Dictionary {} Saves the data as a key-value pair and can access the saved values in the dictionary with the keys instead of the subscript. Dictionaries can contain almost any number of variables, dictionaries, sequences, and tuples. The sequence is the same.The list of Python [] differs from a dictionary in that the

Python data type-List (ADD, modify, delete, query, statistics, values, and sorting), python Data Type A list is one of the most common data types. You can use a list to conveniently store and modify data. Declare an empty list fir

one or three meta-expressionsThe ternary operation is the abbreviation for a simple conditional statement. # if Condition statementIf x > F: print (x) Else: 　　# condition set left, not set rightx if x > y else y # ternary expressionThe ternary operation format for Python is as follows:result= value 1 if x　　# Assign value 1 to the result variable if the condition is true, otherwise assign value 2 to the result variableSecond,

Demonstrate the list generative usage in Python using code instances. 1 sq list If you want to create a list containing 1 to 10 square meters, you can do this: squares = []for x in range(10): squares.append(x**2) This is a simple example, but you can use the list generator

quotation marks for multi-line strings, or multiline commentsJob 1Jump out of the multilayer loop, three-layer cycle, the innermost layer, jumping out of 3 layers,Job 2Shopping Cart Program (knowledge points, loops, lists,)python shopping.pyInput your salary:5000you can buy the following things:1.iphone 58002.coffee3.book4.condom>>: 1can't afford to print, how much is the difference?>>:2can afford to put into the shopping cart, deduct money, while pr

Python ing list learning and python ing List ing is a very useful method. By applying a function to each element in the list to convert data, you can use a policy or method to traverse and compute each element. For example: ? 12345678910111213141516171819202122232

expressionThe builder expression is introduced in python2.4, and you should consider using a generator expression instead of list parsing when the sequence is too long and you need to get only one element at a time. The syntax of a generator expression is the same as a list resolution, except that the generator expression is surrounded by (), not [], as follows:(Expr for Iter_var in iterable)(Expr for Iter

Python data type --- list use, python Data Type List representation: the element can make any data type, such as string, number, Dictionary, list, and variable. Age = 28 Name = ["Frank", "Lee", age, ["Andy", "Troy"] >>> Age = 2 >>> name = ["Frank", "Lee", age, ["Andy", "

Python-List Application-name management system and python-Management System Code: 1 #1 print function prompt 2 print ('=' * 50) 3 print ('name relational system v1.0') 4 print ('1: Add a new name ') 5 print ('2: delete a Name') 6 print ('3: change a Name') 7 print ('4: query a Name') 8 print ('5: exit System ') 9 print (' = '* 50) 10 names = [] # define an empty

List Comprehensions provide a concise-to-create new lists, where each item was the result of an operation applied to EA CH member of an existing list, dictionary or other iterable. Learn how to create your own list comprehensions on this lesson.Sales = [3.14, 7.99, 10.99, 0.99, 1.24 for in sales]With Condiion:Zoo_animals = ['Giraffe','Monkey','Elephant','Lion','

Original blog, reprint please indicate the source--Zhou Xuewei http://www.cnblogs.com/zxouxuewei/I. Build listTo generate list [1, 2, 3, 4, 5, 6, 7, 8, 9, 10], we can use range (1, 11):>>> Range (1) [123456 789]But what if you want to generate [1x1, 2x2, 3x3, ..., 10x10]? Method One is the loop:>>> L = [] for in range (1): .... *>>> l[149 the - Bayi []But the loop is too cumbersome, and the list gene

better by invoking call by need on demand) and is only assigned when retrieved (evaluated), So it's more efficient to use memory when the list is longer. A generator object in Python are something like a lazy list. The elements are only evaluated as soon as your iterate over them. Some notes: 1. It is more consisten

List and looping issues Write a function tag_count whose parameters are listed as a list of strings. The function should return the number of XML tags in the string. XML is a data language similar to HTML. You can determine whether a string is an XML tag, starting with the left angle bracket " You can assume that the list of strings as input does no

How to filter data in lists, dictionaries, collections Renaming of lists (tuples) The realization of Word frequency statistic Sort of dictionary Find common keys for multiple dictionaries How to keep the dictionary in order How to keep track of history (using deque queue) How to filter data in a list, dictionary, collectionProblem Introduction:List: [ -10,2,2,3,-2,7,6,9] Find all non-negative numbersDictionary: {1:90,2:55,

First, List parsingList parsing comes from a functional programming language (Haskell) with the following syntax:Inif cond_expr]The first syntax: Iterate all the contents of iterable, each iteration, put the corresponding content in the iterable into Iter_var, then apply the Iter_var content in the expression, and then generate a list with the calculated value of

map function: Prototype: Map (function, sequence), which is to map a list to another list, How to use: def f (x): Return x**2 L = Range (1,10) Map (f,l) OUT[3]: [1, 4, 9, +, BA] reduce function Prototypes: Reduce (function, sequence, startvalue), which is to generalize a list into one output,How to use: def f2 (x,y): Return X+y Reduce (f1,l) OUT[7]: 45 Reduce (f