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100个Python小技巧(51-100)

前言

目前Python可以说是非常流行，在目前的编程语言中，Python的抽象程度是最高的，是最接近自然语言的，很容易上手。你可以用它来完成很多任务，比如数据科学、机器学习、Web开发、脚本编写、自动化等。

下面，羽峰继续给大家分享100个Python小技巧中剩余的50个，帮助大家更好地了解和学习Python。

51、map()返回一个新对象

map()函数将给定函数应用于可迭代对象(列表、元组等)，然后返回结果(map对象)。

my_list = [1, 2, 3, 4]

squared = map(lambda x: x**2, my_list)

print(list(squared))   # [1, 4, 9, 16]
print(my_list)  # [1, 2, 3, 4]

52、range()的step参数

for number in range(1, 10, 3):
    print(number, end=" ")
# 1 4 7

53、range()默认从0开始

def range_with_zero(number):
    for i in range(0, number):
        print(i, end=' ')

def range_with_no_zero(number):
    for i in range(number):
        print(i, end=' ')

range_with_zero(3)  # 0 1 2
range_with_no_zero(3)  # 0 1 2

54、使用sorted()检查2个字符串是否为相同

def check_if_anagram(first_word, second_word):
    first_word = first_word.lower()
    second_word = second_word.lower()
    return sorted(first_word) == sorted(second_word)

print(check_if_anagram("testinG", "Testing"))  # True
print(check_if_anagram("Here", "Rehe"))  # True
print(check_if_anagram("Know", "Now"))  # False

55、可以在同一个作用域内多次定义一个方法

但是，只有最后一个会被调用，覆盖以前。

def get_address():
    return "First address"

def get_address():
    return "Second address"

def get_address():
    return "Third address"

print(get_address())  # Third address

56、在外部直接访问私有属性

在定义属性或方法时，在属性名或者方法名前增加两个下划线，定义的就是私有属性或方法。

如果想要在外部访问，那么只需要在名称前面加上 '_类名' 变成 '_类名__名称'。

class Engineer:
    def __init__(self, name):
        self.name = name
        self.__starting_salary = 62000

dain = Engineer('Dain')
print(dain._Engineer__starting_salary)  # 62000

57、sort()和sorted()的区别

sort()：对原始列表进行排序

sorted()：返回一个新的排序列表

groceries = ['milk', 'bread', 'tea']

new_groceries = sorted(groceries)
# new_groceries = ['bread', 'milk', 'tea']

print(new_groceries)

# groceries = ['milk', 'bread', 'tea']
print(groceries)

groceries.sort()

# groceries = ['bread', 'milk', 'tea']
print(groceries)

58、定义一个方法，可以调用任意个参数

def get_sum(*arguments):
    result = 0
    for i in arguments:
        result += i
    return result

print(get_sum(1, 2, 3))  # 6
print(get_sum(1, 2, 3, 4, 5))  # 15
print(get_sum(1, 2, 3, 4, 5, 6, 7))  # 28

59、交换字符串中字符的大小写

string = "This is just a sentence."
result = string.swapcase()

print(result)  # tHIS IS JUST A SENTENCE.

60、在类中使用 + 操作符

在两个int数据类型之间使用 + 运算符时，将得到它们的和。

而在两个字符串数据类型之间使用它时，会将其合并。

print(10 + 1)  # 两数相加
print('first' + 'second')  # 字符串相加

这个就是操作符重载，你还可以在类中使用(add)。

class Expenses:
    def __init__(self, rent, groceries):
        self.rent = rent
        self.groceries = groceries

    def __add__(self, other):
        return Expenses(self.rent + other.rent,
                        self.groceries + other.groceries)

april_expenses = Expenses(1000, 200)
may_expenses = Expenses(1000, 300)

total_expenses = april_expenses + may_expenses
print(total_expenses.rent)  # 2000
print(total_expenses.groceries)  # 500

61、在类中使用 < 和 == 操作符

下面定义一个操作重载示例( < 操作符)，使用lt方法。

class Game:
    def __init__(self, score):
        self.score = score

    def __lt__(self, other):
        return self.score < other.score

first = Game(1)
second = Game(2)

print(first < second)  # True

同样的，== 操作符使用eq方法。

class Journey:
    def __init__(self, location, destination, duration):
        self.location = location
        self.destination = destination
        self.duration = duration

    def __eq__(self, other):
        return ((self.location == other.location) and
                (self.destination == other.destination) and
                (self.duration == other.duration))

first = Journey('Location A', 'Destination A', '30min')
second = Journey('Location B', 'Destination B', '30min')

print(first == second)

还有一些其他的定义。

__sub__() for -
__mul__() for *
__truediv__() for /
__ne__() for !=
__ge__() for >=
__gt__() for >

62、为类的对象定义自定义的可打印版本

class Rectangle:
    def __init__(self, a, b):
        self.a = a
        self.b = b

    def __repr__(self):
        return repr('Rectangle with area=' + str(self.a * self.b))

print(Rectangle(3, 4))  # 'Rectangle with area=12'

63、使用super()或父类的名称调用父类的初始化

使用super函数调用父类的初始化方法。

class Parent:
    def __init__(self, city, address):
        self.city = city
        self.address = address

class Child(Parent):
    def __init__(self, city, address, university):
        super().__init__(city, address)
        self.university = university

child = Child('Peking University', 'Fudan University', 'Tsinghua University')
print(child.university)  # Tsinghua University

使用父类的名称调用父类。

class Parent:
    def __init__(self, city, address):
        self.city = city
        self.address = address

class Child(Parent):
    def __init__(self, city, address, university):
        Parent.__init__(self, city, address)
        self.university = university

child = Child('Peking University', 'Fudan University', 'Tsinghua University')
print(child.university)  # Tsinghua University

64、检查字符串是否都是空格

string = "  "
result = string.isspace()

print(result)  # True

65、检查字符串是否都是字母或数字

name = "Password"
print(name.isalnum())  # True

name = "Secure Password "
print(name.isalnum())  # False

name = "S3cur3P4ssw0rd"
print(name.isalnum())  # True

name = "133"
print(name.isalnum())  # True

66、检查字符串是否都是字母

string = "Name"
print(string.isalpha())  # True

string = "Firstname Lastname"
print(string.isalpha())  # False

string = "P4ssw0rd"
print(string.isalpha())  # False

67、根据参数删除字符

从右侧开始。

string = "This is a sentence with       "
print(string.rstrip())  # "This is a sentence with"

string = "this here is a sentence…..,,,,aaaaasd"
print(string.rstrip(".,dsa"))  # "this here is a sentence"

同样的，左侧也能操作。

string = "ffffffffFirst"
print(string.lstrip("f"))  # First

68、检查字符串是否为数字

string = "seven"
print(string.isdigit())  # False

string = "1337"
print(string.isdigit())  # True

string = "5a"
print(string.isdigit())  # False

string = "2**5"
print(string.isdigit())  # False

69、检查字符串是否为中文数字

# 42673
string = "四二六七三"

print(string.isdigit())  # False
print(string.isnumeric())  # True

70、检查字符串是否所有单词都是大写开头

string = "This is a sentence"
print(string.istitle())  # False

string = "10 Python Tips"
print(string.istitle())  # True

string = "How to Print A String in Python"
# False
print(string.istitle())

string = "PYTHON"
print(string.istitle())  # False

71、在元组中使用负索引

numbers = (1, 2, 3, 4)

print(numbers[-1])  # 4
print(numbers[-4])  # 1

72、在元组中嵌套列表和元组

mixed_tuple = (("a"*10, 3, 4), ['first', 'second', 'third'])

print(mixed_tuple[1])  # ['first', 'second', 'third']
print(mixed_tuple[0])  # ('aaaaaaaaaa', 3, 4)

73、快速统计元素在列表中出现的次数

names = ["Besim", "Albert", "Besim", "Fisnik", "Meriton"]

print(names.count("Besim"))  # 2

74、使用slice()获取元素

使用slice()获取最后n个元素。

my_list = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
slicing = slice(-4, None)
print(my_list[slicing])  # [4, 5, 6]

print(my_list[-3])  # 4

使用slice()做切片任务。

string = "Data Science"

slice_object = slice(5, None)
print(string[slice_object])   # Science

75、计算元素在元组中出现的次数

my_tuple = ('a', 1, 'f', 'a', 5, 'a')

print(my_tuple.count('a'))  # 3

76、if语句中的多个条件

math_points = 51
biology_points = 78
physics_points = 56
history_points = 72

my_conditions = [math_points > 50, biology_points > 50,
                 physics_points > 50, history_points > 50]

if all(my_conditions):
    print("Congratulations! You have passed all of the exams.")
else:
    print("I am sorry, but it seems that you have to repeat at least one exam.")
# Congratulations! You have passed all of the exams.

77、使用uuid模块生成唯一ID

UUID代表唯一标识符。

import uuid

# 根据主机ID、序列号和当前时间生成UUID
print(uuid.uuid1())  # 308490b6-afe4-11eb-95f7-0c4de9a0c5af

# 生成一个随机UUID
print(uuid.uuid4())  # 93bc700b-253e-4081-a358-24b60591076a

78、通过索引获取子元组

my_tuple = (1, 2, 3, 4, 5, 6, 7, 8, 9, 10)

print(my_tuple[3:])  # (4, 5, 6, 7, 8, 9, 10)

79、将列表、集合、字典中所有元素删除

my_list = [1, 2, 3, 4]
my_list.clear()
print(my_list)  # []

my_set = {1, 2, 3}
my_set.clear()
print(my_set)  # set()

my_dict = {"a": 1, "b": 2}
my_dict.clear()
print(my_dict)  # {}

80、合并集合

使用union()方法，返回一个新集合。

first_set = {4, 5, 6}
second_set = {1, 2, 3}

print(first_set.union(second_set))  # {1, 2, 3, 4, 5, 6}

还可以使用update()方法，将第二个集合的元素插入到第一个集合中去。

first_set = {4, 5, 6}
second_set = {1, 2, 3}

first_set.update(second_set)

print(first_set)  # {1, 2, 3, 4, 5, 6}

81、在函数里输出结果

def is_positive(number):
    print("Positive" if number > 0 else "Negative")  # Positive

is_positive(-3)

82、获取元组中元素的索引

my_tuple = ('a', 1, 'f', 'a', 5, 'a')

print(my_tuple.index('f'))  #  2

83、在一个if语句中，至少满足多个条件中的一个

math_points = 40
biology_points = 78
physics_points = 56
history_points = 72

my_conditions = [math_points > 50, biology_points > 50,
                 physics_points > 50, history_points > 50]

if any(my_conditions):
    print("Congratulations! You have passed all of the exams.")
else:
    print("I am sorry, but it seems that you have to repeat at least one exam.")
# Congratulations! You have passed all of the exams.

84、任何非空字符串都为True

print(bool("Non empty"))  # True
print(bool(""))  # False

85、使用itertools中的count计算元素的数量

from itertools import count

my_vowels = ['a', 'e', 'i', 'o', 'u', 'A', 'E', 'I', 'O', 'U']

current_counter = count()

string = "This is just a sentence."

for i in string:
    if i in my_vowels:
        print(f"Current vowel: {i}")
        print(f"Number of vowels found so far: {next(current_counter)}")

输出如下。

Current vowel: i
Number of vowels found so far: 0
Current vowel: i
Number of vowels found so far: 1
Current vowel: u
Number of vowels found so far: 2
Current vowel: a
Number of vowels found so far: 3
Current vowel: e
Number of vowels found so far: 4
Current vowel: e
Number of vowels found so far: 5
Current vowel: e
Number of vowels found so far: 6

86、None、False、0都为False

print(bool(False))  # False
print(bool(None))  # False
print(bool(0))  # False

87、在函数中使用全局变量

在函数无法直接修改全局变量的值。

string = "string"

def do_nothing():
  string = "inside a method"

do_nothing()

print(string)  # string

可通过修饰符global，修改全局变量的值。

string = "string"

def do_nothing():
    global string
    string = "inside a method"

do_nothing()

print(string)  # inside a method

88、计算字符串或列表中元素的数量

使用collections中的Counter计算字符串或列表中元素的数量。

from collections import Counter

result = Counter("Banana")
print(result)  # Counter({'a': 3, 'n': 2, 'B': 1})

result = Counter([1, 2, 1, 3, 1, 4, 1, 5, 1, 6])
print(result)  # Counter({1: 5, 2: 1, 3: 1, 4: 1, 5: 1, 6: 1})

89、检查2个字符串是否为相同

可以使用Counter()方法。

from collections import Counter

def check_if_anagram(first_string, second_string):
    first_string = first_string.lower()
    second_string = second_string.lower()
    return Counter(first_string) == Counter(second_string)

print(check_if_anagram('testinG', 'Testing'))  # True
print(check_if_anagram('Here', 'Rehe'))  # True
print(check_if_anagram('Know', 'Now'))  # False

可以使用sorted()方法。

def check_if_anagram(first_word, second_word):
    first_word = first_word.lower()
    second_word = second_word.lower()
    return sorted(first_word) == sorted(second_word)

print(check_if_anagram("testinG", "Testing"))  # True
print(check_if_anagram("Here", "Rehe"))  # True
print(check_if_anagram("Know", "Now"))  # False

90、任何非空列表、元组、字典都为True

print(bool([]))  # False
print(bool(set([])))  # False

print(bool({}))  # False
print(bool({"a": 1}))  # True

91、对字符串或列表的元素进行次数排序

collections模块的Counter()，默认情况下是不会根据元素的频率对它们进行排序的。

from collections import Counter

result = Counter([1, 2, 3, 2, 2, 2, 2])
print(result)  # Counter({2: 5, 1: 1, 3: 1})
print(result.most_common())  # [(2, 5), (1, 1), (3, 1)]