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This article mainly explains the "what practical Python skills", the content of the explanation is simple and clear, easy to learn and understand, the following please follow the editor's ideas slowly in depth, together to study and learn "what practical Python skills" bar!

1. Repetitive element determination

The following method checks to see if there are duplicate elements in a given list, which uses the set () function to remove all duplicate elements.

Def all_unique (lst): return len (lst) = = len (set (lst)) x = [1, False all_unique, 2, 2, 3, 3, 3, 4, 5] y = [1, 2, 3, 5] all_unique (x) # False all_unique (y) # True

two。 Determination of character element composition

Check whether the constituent elements of the two strings are the same.

From collections import Counter def anagram (first, second): return Counter (first) = = Counter (second) anagram ("abcd3", "3acdb") # True

3. Memory footprint

The following code block checks the memory occupied by the variable variable.

Import sys variable = 30 print (sys.getsizeof (variable)) # 24

4. Byte occupancy

The following code block checks the number of bytes occupied by the string.

Def byte_size (string): return (len (string.encode ('utf-8') byte_size ('') # 4 byte_size ('Hello World') # 11

5. Print N-th string

This code block can print a string N times without a loop statement.

N = 2; s = "Programming"; print (s * n); # ProgrammingProgramming

6. Uppercase first letter

The following code block uses the title () method to capitalize the first letter of each word in the string.

S = "programming is awesome" print (s.title ()) # Programming Is Awesome

7. Divide into blocks

Given the specific size, define a function to cut the list according to that size.

From math import ceil def chunk (lst, size): return list (map (lambda x: lst [x * size:x * size + size], list (range (0, ceil (len (lst) / size) chunk)

8. Compress

This method removes Boolean values, such as (False,None,0, ""), which uses the filter () function.

Def compact (lst): return list (filter (bool, lst)) compact ([0,1, False, 2,', 3, 'axiom,' Aguilar, 34]) # [1, 2, 3, 'axiang,' aforementioned, 34]

9. Unpack

The following code snippet unwraps the packaged paired list into two different tuples.

Array = [['averse,' b'], ['centering,' d'], ['eBay,' f']] transposed = zip (* array) print (transposed) # [('axiang,' censor,'e'), ('baked,' dumped,'f')]

10. Chain contrast

We can use different operators to compare multiple different elements in a single line of code.

A = 3 print (2

< a < 8) # True print(1 == a < 2) # False 11. 逗号连接 下面的代码可以将列表连接成单个字符串，且每一个元素间的分隔方式设置为了逗号。 hobbies = ["basketball", "football", "swimming"] print("My hobbies are: " + ", ".join(hobbies)) # My hobbies are: basketball, football, swimming 12. 元音统计 以下方法将统计字符串中的元音 (‘a’, ‘e’, ‘i’, ‘o’, ‘u’) 的个数，它是通过正则表达式做的。 import re def count_vowels(str): return len(re.findall(r'[aeiou]', str, re.IGNORECASE)) count_vowels('foobar') # 3 count_vowels('gym') # 0 13. 首字母小写 如下方法将令给定字符串的第一个字符统一为小写。 def decapitalize(string): return str[:1].lower() + str[1:] decapitalize('FooBar') # 'fooBar' decapitalize('FooBar') # 'fooBar' 14. 展开列表 该方法将通过递归的方式将列表的嵌套展开为单个列表。 def spread(arg): ret = [] for i in arg: if isinstance(i, list): ret.extend(i) else: ret.append(i) return ret def deep_flatten(lst): result = [] result.extend( spread(list(map(lambda x: deep_flatten(x) if type(x) == list else x, lst)))) return result deep_flatten([1, [2], [[3], 4], 5]) # [1,2,3,4,5] 15. 列表的差 该方法将返回第一个列表的元素，其不在第二个列表内。如果同时要反馈第二个列表独有的元素，还需要加一句 set_b.difference(set_a)。 def difference(a, b): setset_a = set(a) setset_b = set(b) comparison = set_a.difference(set_b) return list(comparison) difference([1,2,3], [1,2,4]) # [3] 16. 通过函数取差 如下方法首先会应用一个给定的函数，然后再返回应用函数后结果有差别的列表元素。 def difference_by(a, b, fn): b = set(map(fn, b)) return [item for item in a if fn(item) not in b] from math import floor difference_by([2.1, 1.2], [2.3, 3.4],floor) # [1.2] difference_by([{ 'x': 2 }, { 'x': 1 }], [{ 'x': 1 }], lambda v : v['x']) # [ { x: 2 } ] 17. 链式函数调用 你可以在一行代码内调用多个函数。 def add(a, b): return a + b def subtract(a, b): return a - b a, b = 4, 5 print((subtract if a >

B else add) (a, b)) # 9

18. Check for duplicates

The following code checks the two lists for duplicates.

Def has_duplicates (lst): return len (lst)! = len (set (lst)) x = [1, True has_duplicates, 3, 4, 5] y = [1, 2, 3, 5] has_duplicates (x) # True has_duplicates (y) # False

19. Merge two dictionaries

The following method will be used to merge two dictionaries.

Def merge_two_dicts (a, b): C = a.copy () # make a copy of a c.update (b) # modify keys and values of a with the ones from b return c a = {"x": 1, "y": 2} b = {"y": 3, "z": 4} print (merge_two_dicts (a, b)) # {"y": 3, "x": 1, "z": 4}

In Python 3.5 or later, we can also merge dictionaries in the following ways:

Def merge_dictionaries (a, b) return {* * a, * * b} a = {"x": 1, "y": 2} b = {"y": 3,'z ": 4} print (merge_dictionaries (a, b)) # {" x ": 3," x: 1, "z: 4}

20. Convert two lists into dictionaries

The following method will convert two lists into a single dictionary.

Def to_dictionary (keys, values): return dict (zip (keys, values)) keys = ["a", "b", "c"] values = [2,3,4] print (to_dictionary (keys, values)) # {'averse: 2,' cession: 4, 'baked: 3}

21. Use enumerations

We often use For loops to iterate through a list, and we can also enumerate the indexes and values of the list.

twenty-two。 Execution time

The following code block can be used to calculate the time it takes to execute a particular code.

Import time start_time = time.time () a = 1b = 2c = a + b print (c) # 3 end_time = time.time () total_time = end_time-start_time print ("Time:", total_time) # ('Time:', 1.1205673217773438e-05)

23. Try else

We can also add an else clause when using the try/except statement, which will be run if no error is triggered.

Try: 2: 3 except TypeError: print ("An exception was raised") else: print ("Thank God, no exceptions were raised.") # Thank God, no exceptions were raised.

24. Element frequency

The following method takes the most common elements in the list based on the frequency of the elements.

25. Palindromes sequence

The following method checks whether the given string is a palindrome sequence. It first converts all letters to lowercase and removes non-English alphabet symbols. Finally, it compares whether the string is equal to the reverse string, which is represented as a palindrome sequence.

Def palindrome (string): from re import sub s = sub ('[W_]','', string.lower ()) return s = s [::-1] palindrome ('taco cat') # True

twenty-six。 Calculators that do not use if-else

This code can add, subtract, multiply, divide, and exponentiate without using conditional statements, which is realized through the data structure of dictionary:

twenty-seven。 Shuffle

This algorithm scrambles the order of the list elements, and it mainly sorts the new list through the Fisher-Yates algorithm:

From copy import deepcopy from random import randint def shuffle (lst): temp_lst = deepcopy (lst) m = len (temp_lst) while (m): M-= 1 I = randint (0, m) temp_lst [m], temp_ LST [I] = temp_lst [I], temp_ LST [m] return temp_lst foo = [1je 2jue 3] shuffle (foo) # [2Jing 3jue 1], foo = [1Jing 2jue 3]

twenty-eight。 Expand the list

Expand all elements in the list, including sublists, into a list.

Def spread (arg): ret = [] for i in arg: if isinstance (I, list): ret.extend (I) else: ret.append (I) return ret spread

twenty-nine。 Swap values can exchange the values of two variables without additional operations

Def swap (a, b): return b, an a, b =-1, 14 swap (a, b) # (14,-1) spread ([1, 2, 5, 6], [7], 8, 9]) # [1, 2, 4, 4, 5, 7, 8]

thirty。 The dictionary default value takes the corresponding Value value through Key, and you can set the default value in the following ways. If the get () method does not set the default value, it returns None if it encounters a Key that does not exist.

D = {'averse: 1,' baked: 2} print (d.get ('clocked, 3)) # 3 Thank you for your reading, the above is the content of "what are the practical Python skills". After the study of this article, I believe you have a deeper understanding of what practical Python skills there are, and the specific use needs to be verified in practice. Here is, the editor will push for you more related knowledge points of the article, welcome to follow!

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