Python常用技巧实例分析

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1.字符串反转

使用Python切片反转字符串：

# Reversing a string using slicing my_string = "ABCDE"reversed_string = my_string[::-1] print(reversed_string) # Output# EDCBA

2.每个单词的第一个字母大写

使用title函数方法：

my_string = "my name is chaitanya baweja" # using the title() function of string classnew_string = my_string.title() print(new_string) # Output# My Name Is Chaitanya Baweja

3. 字符串查找唯一元素

使用集合的概念查找字符串的唯一元素:

my_string = "aavvccccddddeee" # converting the string to a settemp_set = set(my_string) # stitching set into a string using joinnew_string = ''.join(temp_set) print(new_string) # output# cdvae

4.重复打印字符串和列表n次

你可以使用乘法符号（*）打印字符串或列表多次：

n = 3 # number of repetitions my_string = "abcd"my_list = [1,2,3] print(my_string*n)# abcdabcdabcd print(my_list*n)# [1,2,3,1,2,3,1,2,3]

5.列表生成

# Multiplying each element in a list by 2 original_list = [1,2,3,4] new_list = [2*x for x in original_list] print(new_list)# [2,4,6,8]

6.变量交换

a = 1b = 2 a, b = b, a print(a) # 2print(b) # 1

7.字符串拆分为子字符串列表

使用.split()函数：

string_1 = "My name is Chaitanya Baweja"string_2 = "sample/ string 2" # default separator ' 'print(string_1.split())# ['My', 'name', 'is', 'Chaitanya', 'Baweja'] # defining separator as '/'print(string_2.split('/'))# ['sample', ' string 2']

8.多个字符串组合为一个字符串

list_of_strings = ['My', 'name', 'is', 'Chaitanya', 'Baweja'] # Using join with the comma separatorprint(','.join(list_of_strings)) # Output# My,name,is,Chaitanya,Baweja

9.检测字符串是否为回文

my_string = "abcba" if my_string == my_string[::-1]:    print("palindrome")else:    print("not palindrome") # Output# palindrome

10. 统计列表中元素的次数

# finding frequency of each element in a listfrom collections import Counter my_list = ['a','a','b','b','b','c','d','d','d','d','d']count = Counter(my_list) # defining a counter object print(count) # Of all elements# Counter({'d': 5, 'b': 3, 'a': 2, 'c': 1}) print(count['b']) # of individual element# 3 print(count.most_common(1)) # most frequent element# [('d', 5)]

11.判断两个字符串是否为Anagrams

Anagrams的含义为两个单词中，每个英文单词（不含大小写）出现的次数相同，使用Counter类判断两个字符串是否为Anagrams。

from collections import Counter str_1, str_2, str_3 = "acbde", "abced", "abcda"cnt_1, cnt_2, cnt_3  = Counter(str_1), Counter(str_2), Counter(str_3) if cnt_1 == cnt_2:    print('1 and 2 anagram')if cnt_1 == cnt_3:    print('1 and 3 anagram') # output# 1 and 2 anagram

12. 使用try-except-else-block模块

except获取异常处理：

a, b = 1,0 try:    print(a/b)    # exception raised when b is 0except ZeroDivisionError:    print("division by zero")else:    print("no exceptions raised")finally:    print("Run this always") # output# division by zero# Run this always

13. 使用枚举函数得到key/value对

my_list = ['a', 'b', 'c', 'd', 'e'] for index, value in enumerate(my_list):    print('{0}: {1}'.format(index, value)) # 0: a# 1: b# 2: c# 3: d# 4: e

14.检查对象的内存使用情况

import sys num = 21 print(sys.getsizeof(num)) # In Python 2, 24# In Python 3, 28

15.合并字典

dict_1 = {'apple': 9, 'banana': 6}dict_2 = {'banana': 4, 'orange': 8} combined_dict = {**dict_1, **dict_2} print(combined_dict)# Output# {'apple': 9, 'banana': 4, 'orange': 8}

16.计算执行一段代码所花费的时间

使用time类计算运行一段代码所花费的时间：

import time start_time = time.time()# Code to check followsfor i in range(10**5):    a, b = 1,2    c = a+ b# Code to check endsend_time = time.time()time_taken_in_micro = (end_time- start_time)*(10**6) print(time_taken_in_micro) # output# 18770.217895507812

17. 列表展开

from iteration_utilities import deepflatten # if you only have one depth nested_list, use thisdef flatten(l):  return [item for sublist in l for item in sublist] l = [[1,2,3],[3]]print(flatten(l))# [1, 2, 3, 3] # if you don't know how deep the list is nestedl = [[1,2,3],[4,[5],[6,7]],[8,[9,[10]]]] print(list(deepflatten(l, depth=3)))# [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

18. 列表采样

import random my_list = ['a', 'b', 'c', 'd', 'e']num_samples = 2 samples = random.sample(my_list,num_samples)print(samples)# [ 'a', 'e'] this will have any 2 random values

19.数字化

将整数转化成数字列表

num = 123456 # using maplist_of_digits = list(map(int, str(num))) print(list_of_digits)# [1, 2, 3, 4, 5, 6] # using list comprehensionlist_of_digits = [int(x) for x in str(num)] print(list_of_digits)# [1, 2, 3, 4, 5, 6]

20.检查列表元素的唯一性

检查列表中每个元素是否为唯一的：

def unique(l):    if len(l)==len(set(l)):        print("All elements are unique")    else:        print("List has duplicates") unique([1,2,3,4])# All elements are unique unique([1,1,2,3])# List has duplicates

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