20 Essential Python Tricks to Boost Your Coding Efficiency

1. String reversal

str1 = "qwert"
rev_str1 = str1[::-1]
# output: trewq

2. Capitalize first letters

str1 = "this is a book"
print(str1.title())
# This Is A Book

3. Find unique characters in a string

str1 = "aabbccccdddd"
set1 = set(str1)
new_str = ''.join(set1)
print(new_str)

4. Repeat strings or lists

i = 4
str1 = "abcd"
list1 = [1, 2]
print(str1 * i)   # abcdabcdabcdabcd
print(list1 * i)   # [1, 2, 1, 2, 1, 2, 1, 2]

5. List comprehension

list1 = [1, 2, 3]
new_list1 = [2 * i for i in list1]
# [2, 4, 6]

6. Swap variables without a temporary

x = 1
y = 2
x, y = y, x
print(x)  # 2
print(y)  # 1

7. Split a string into a list of substrings

str1 = "This is a book"
str2 = "test/ str 2"
print(str1.split())          # ['This', 'is', 'a', 'book']
print(str2.split('/'))       # ['test', ' str 2']

8. Join a list of strings into a single string

list_str = ['This', 'is', 'a', 'book']
print(','.join(list_str))   # This,is,a,book

9. Check for palindrome strings

str1 = "qqaabb"
if str1 == str1[::-1]:
    print("回文")
else:
    print("不是")
# 不是

10. Count elements in a list using Counter

from collections import Counter
list1 = ['a', 'b', 'a', 'c', 'c', 'c']
count = Counter(list1)
print(count)
print(count['b'])
print(count.most_common(1))

11. Determine if two strings are anagrams

s1, s2, s3 = "acbde", "abced", "abcda"
c1, c2, c3 = Counter(s1), Counter(s2), Counter(s3)
if c1 == c2:
    print('1和2是异序词')
if c1 == c3:
    print('1和3是异序词')

12. Use try‑except‑else‑finally blocks

a, b = 1, 0
try:
    print(a / b)
except ZeroDivisionError:
    print("除数为0")
else:
    print("不存在异常")
finally:
    print("此段总是会执行")

13. Enumerate to get index/value pairs

list1 = ['a', 'b', 'c', 'd', 'e']
for idx, val in enumerate(list1):
    print('{0}:{1}'.format(idx, val))
# 0:a
# 1:b
# 2:c
# 3:d
# 4:e

14. Get memory size of an object

import sys
num = 21
print(sys.getsizeof(num))

15. Merge two dictionaries

dic1 = {'app': 9, 'banana': 6}
dic2 = {'banana': 4, 'orange': 8}
com_dict = {**dic1, **dic2}
# {'app': 9, 'banana': 4, 'orange': 8}

16. Measure code execution time

import time
s_time = time.time()
a, b = 1, 2
c = a + b
e_time = time.time()
time_taken_in_micro = (e_time - s_time) * (10**6)
print("程序运行的毫秒：{0} ms".format(time_taken_in_micro))

17. Flatten nested lists

from iteration_utilities import deepflatten
# shallow flatten
list1 = [[1, 2, 3], [3]]
print([item for sublist in list1 for item in sublist])
# deep flatten (unknown depth)
l = [[1,2,3],[4,[5]],[6,7]], [8,[9,[10]]]
print(list(deepflatten(l, depth=3)))

18. Random sampling from a list

import random
list1 = ['a', 'b', 'c', 'd', 'e']
ns = 2
samples = random.sample(list1, ns)
print(samples)  # e.g., ['a', 'c']

19. Convert an integer to a list of digits

nums = 123456
digit_list = list(map(int, str(nums)))
print(digit_list)  # [1,2,3,4,5,6]
# or using list comprehension
digit_list = [int(x) for x in str(nums)]
print(digit_list)

20. Check for uniqueness in a list

def unique(l):
    if len(l) == len(set(l)):
        print("所有元素是唯一的")
    else:
        print("存在重复")
unique([1,2,3,4])   # 所有元素是唯一的
unique([1,1,3,4])   # 存在重复