Python学习之12个常用基础语法详解

目录

• 前言
• 1.多个字符串组合为一个字符串
• 2.字符串拆分为子字符串列表
• 3.统计列表中元素的次数
• 4.使用try-except-else-block模块
• 5.使用枚举函数得到key/value对
• 6.检查对象的内存使用情况
• 7.合并字典
• 8.计算执行一段代码所花费的时间
• 9.列表展开
• 10.列表采样
• 11.数字化
• 12.检查列表元素的唯一性

前言

前几天写了一篇关于python高级语法的文章：python进阶从青铜到王者一定会用上的Python技巧。

有读者私信说：怎么看自己是不是入门python了呢？ 开发中高频python基础语法有哪些呢？

下面通过12个小案例，包含了日常开发中非常实用的语法，大家一起来检验下你会几个呢？

1. 多个字符串组合为一个字符串

list_of_strings = ['My', 'name', 'is', 'Dragon']

# Using join with the comma separator
print(' '.join(list_of_strings))

# Output
# My name is Dragon

2. 字符串拆分为子字符串列表

string_1 = "My name is Dragon"
string_2 = "sample/ string 2"

# default separator ' '
print(string_1.split())
# ['My', 'name', 'is', 'Dragon']

# defining separator as '/'
print(string_2.split('/'))
# ['sample', ' string 2']

3. 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)]

4. 使用try-except-else-block模块

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

5. 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

6. 检查对象的内存使用情况

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

7. 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}

8. 计算执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
# 28770.217895507812

9. 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]

10. 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

11. 数字化

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]

12. 检查列表元素的唯一性

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

到此这篇关于Python学习之12个常用基础语法详解的文章就介绍到这了,更多相关Python基础语法内容请搜索我们以前的文章或继续浏览下面的相关文章希望大家以后多多支持我们！