Shulou(Shulou.com)05/31 Report--

In this article, the editor introduces in detail "how to use Python". The content is detailed, the steps are clear, and the details are handled properly. I hope this article "how to use Python" can help you solve your doubts.

What is the deduction type?

Deduction is a simplified use of for loops, which uses deduction to traverse data from an iterable object into a container. To put it simply, it is a process and way of traversing all the data in an iterable object with a single for loop statement, and then processing the traversed data into the corresponding container.

And deriving a similar function is the ternary operator, which is a simplified method for the use of conditional judgment statements.

Syntax:

Val for val in Iterable

Is the data stored in the container + for loop statement

There are three ways to express the deductive form, which are wrapped in corresponding symbols:

List derivation test: [val for val in Iterable]

Set derivation: {val for val in Iterable}

Dictionary derivation: {x for y in Iterable}

List derivation:

The list is pushed to the formula, and the traversed data will eventually become a list data.

Basic grammar

10 pieces of data are stored in the list:

# conventional writing lst = [] for i in range (1,11): lst.append (I) print (lst) # [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] # derivation lst = [i for i in range (1, 11)] print (lst) # [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] other usage

Single cycle push type:

# processing data in the container: [1,2,3,4,5]-> [3,6,9,12,15] lst = [1,2,3,4,5] # Common new_lst = [] for i in lst: res = I * 3 new_lst.append (res) print (new_lst) # [3,6,9,12 15] # deductive new_lst = [I * 3 for i in lst] print (new_lst) # [3, 6, 9, 12, 15]

Single-loop derivation with judgment conditions:

# filter out odd numbers lst = [0,1,2,3,4,5,6,7,8,9] # Common new_lst = [] for i in lst: if I% 2 = = 1: new_lst.append (I) print (new_lst) # [1,3,5,7 9] # deductive writing # deductive use of individual branches can only be done after the end of the for statement using new_lst = [i for i in lst if i% 2 = = 1] print (new_lst) # [1, 3, 5, 7, 9]

Multi-cycle derivation:

# the sum of the data in the two lists lst = [1,2,3] lst1 = [11,22,33] # Common method new_lst = [] for i in lst: for j in lst1: res = I + j new_lst.append (res) print (new_lst) # [12, 23, 34, 13, 24, 35, 14, 25 36] # deductive writing new_lst = [I + j for i in lst for j in lst1] print (new_lst) # [12, 23, 34, 13, 24, 35, 14, 25, 36] list guided exercises

1. Change the data in the dictionary into the style of ['xylene', 'yawning', 'zealc']

{"x": "A", "y": "B", "z": "C'}"

2. Change the elements used into pure lowercase

["ADDD", "dddDD", "DDaa", "sss"]

3. X is an even number between 0 and 5, and y is an odd number between 0 and 5. Make xMagol y into tuples together and put them in the list.

4. Use list deduction to make all the operations in 99 multiplication tables.

5. Find the product of matrices and elements in M _ ~ N

M = [1, 2, 3], [4, 5, 6], [7, 8, 9]]

N = [2, 2, 2], [3, 3, 3, 4]

# one of the solutions to the fifth problem # = > realization effect 1 [2, 4, 6, 12, 15, 18, 28, 32, 36] # = > realization effect 2 [[2, 4, 6], [12, 15, 18], [28, 32] 36]] # implementation effect 1lst_new = [] for i in range (len (M)): for j in range (len (N)): res = M [I] [j] * N [I] [j] lst_new.append (res) print (lst_new) # deductive writing res = [M [I] [j] * NI] [j] for i in range (len (M)) for j in range (len (N))] print (res) # implementation effect 2lst_new = [] for i in range (len (M)): lst_new2 = [] for j in range (len (N)): res = M [I] [j] * N [I] [j] lst_new2.append (res) lst_new .append (lst_new2) print (lst_new) # inference res = [[M [I] [j] * N [I] [j] for j in range (len (M))] for i in range (len (N))] print (res) set derivation

The use of set derivation and list derivation is basically the same, but the outer braces are included, and the resulting data is a collection.

Example:

Case: for people aged 18 to 21 with deposits greater than or equal to 5000 and less than or equal to 5500, the card format is: honorable VIP card Lao X (surname) Otherwise, the card opening format is as follows: foot-pinching man Lao X (surname), count the types of cards opened [{"name": "Liu Xinwei", "age": 18, "money": 10000}, {"name": "Liu Cong", "age": 19, "money": 5100}, {"name": "Liu Zihao", "age": 20, "money": 4800} {"name": "Kong Xiangqun", "age": 21, "money": 2000}, {"name": "Song Yunjie", "age": 18, "money": 20}] # conventional writing setvar = set () for i in lst: if (18

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.