Python常用的20个技巧

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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  
exceptZeroDivisionError:  
    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 inrange(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\_utilitiesimport deepflatten  
  
\# if you only have one depth nested\_list, use this  
defflatten(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

总结

• 最后希望你编程学习上不急不躁,按照计划有条不紊推进,把任何一件事做到极致,都是不容易的,加油,努力！相信自己！

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