你需要掌握的20个Python常用技巧

目录

• 1.字符串反转
• 2.每个单词的第一个字母大写
• 3.字符串查找唯一元素
• 4.重复打印字符串和列表n次
• 5.列表生成
• 6.变量交换
• 7.字符串拆分为子字符串列表
• 8.多个字符串组合为一个字符串
• 9.检测字符串是否为回文
• 10.统计列表中元素的次数
• 11.判断两个字符串是否为Anagrams
• 12.使用try-except-else-block模块
• 13.使用枚举函数得到key/value对
• 14.检查对象的内存使用情况
• 15.合并字典
• 16.计算执行一段代码所花费的时间
• 17.列表展开
• 18.列表采样
• 19.数字化
• 20.检查列表元素的唯一性

Python的可读性和简单性是其广受欢迎的两大原因，本文介绍20个常用的Python技巧来提高代码的可读性，并能帮助你节省大量时间，下面的技巧将在你的日常编码练习中非常实用。

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 class
new_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 set
temp_set = set(my_string)
 
# stitching set into a string using join
new_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 = 1
b = 2
 
a, b = b, a
 
print(a) # 2
print(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 separator
print(\',\'.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 list
from 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 0
except 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 follows
for i in range(10**5):
    a, b = 1,2
    c = a+ b
# Code to check ends
end_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 this
def 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 nested
l = [[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 map
list_of_digits = list(map(int, str(num)))
 
print(list_of_digits)
# [1, 2, 3, 4, 5, 6]
 
# using list comprehension
list_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

以上就是你需要掌握的20个Python常用技巧的详细内容，更多关于Python技巧的资料请关注其它相关文章！