【python】python常用函数 (基础操作都给你列了~)-优快云博客

这里写目录标题

金额计算

示例

from decimal import Decimal,ROUND_DOWN

price = Decimal("10.55")
coupon = Decimal("0.001")
number = Decimal("2")

final_price = (price - coupon).quantize(Decimal('0.00'), rounding=ROUND_DOWN )# 10.54
total_price = (final_price * number).quantize(Decimal('0.00'), rounding=ROUND_DOWN )
print(total_price)  # 输出: 21.08

字符串

获取字符串长度

str = "123456"
str2 = "衔接文字"
print(len(str)) # 6

转为整型

str = "123456"
print(int(str))

切割字符串

str = "123456"
print(str[1:4])# 234
print(str[:4])# 1234
print(str[:-1])# 12345
print(str[-2:-1])# 5

替换指定字符串

str = "123456"
print(str.replace('23','45')) # 145456

两个字符串衔接

str = "123456"
str2 = "衔接文字"
print(str + str2)  # 123456衔接文字
print("--".join([str, str2]))  # 123456--衔接文字
print(f"{str}~~{str2}")  # 123456~~衔接文字

根据指定字符串切割成列表

str3 = "1,2,3"
print(str3.split(','))# ['1', '2', '3']

循环字符串中每个字符

for i in str:
    print(i)#1

列表

判断列表中的元素是否存在

list = [1, 2, 3]
print(2 in list)# True

获取元素出现的次数

a1 = [1,2,3,3,3,3]
print(a1.count(3))# 4

获取list元素的值

list1 = ['a', 'b', 'c']
print(list[0])# a

循环list的每一个元素并修改元素值

list = ['a', 'b', 'c']
for key, value in enumerate(list):
    list[key] = value + "1"
print(list)# ['a1', 'b1', 'c1']

将列表元素组成字符串

list = ['a', 'b', 'c']
print(','.join(list))  # a,b,c

列表元素内大小排序

# 正序
list2 = [3,2,4]
list2.sort()
print(list2)# [2, 3, 4]
# 倒序
list2 = [3,2,4]
list2.sort(reverse=True)
print(list2)# [4, 3, 2]

获取列表长度

list1 = ['a', 'b', 'c']
print(len(list1))# 3

增加元素

list1 = ['a', 'b', 'c']

list1.append('d')
print(list1)# ['a', 'b', 'c', 'd']

增加元素（指定位置）

list1 = ['b', 'd', 'e']

list1.insert(1,'c')#1指的是在第1的位置
print(list1)# ['b', 'c', 'd', 'e']

修改list元素的值

list = ['a', 'b', 'c']
list[0] = 'd'
print(list)  # ['d', 'b', 'c']

删除元素（根据元素值）

list1 = ['a', 'b', 'c','a']

if 'a' in list1:
    list1.remove('a')
print(list1)# ['b', 'c', 'a']

删除某个元素（根据索引）

list1 = ['a', 'b', 'c','a']
print(list1.pop(1))# b
print(list1)# ['a', 'c', 'a']

列表合并

list_1 = [1, 2]
list_2 = [3, 4]
print(list_1 + list_2)  # 第一种[1, 2, 3, 4]
list_1.extend(list_2)  # 第二种
print(list_1)  # [1, 2, 3, 4]

字典

新增键值对

dict1 = {"name": "qjx"}
# 增加键值对
dict1['age'] = 18#第一种
dict1.update({"city": "深圳市"})#第二种
print(dict1)  # {'name': 'qjx', 'age': 18, 'city': '深圳市'}

修改键值对

dict1 = {"name": "qjx"}

dict1['name']="qjx1"
print(dict1)# {'name': 'qjx1'}

修改或新增键值对

dict1 = {"name": "qjx", "age": 18}

dict1.update({"age": 28, "sex": "female"})
print(dict1)# {'name': 'qjx', 'age': 28, 'sex': 'female'}

删除键值对

dict1 = {"name": "qjx", "school": {"school_name": "爱华小学", "class_name": "二年三班"}}
if "school" in dict1:
    del dict1['school']
print(dict1)# {'name': 'qjx'}

删除键值对(删除并返回)

dict1 = {"name": "qjx", "school": {"school_name": "爱华小学", "class_name": "二年三班"}}
print(dict1.pop("school"))#{'school_name': '爱华小学', 'class_name': '二年三班'}
print(dict1)# {'name': 'qjx'}

判断字典中是否存在指定键

dict1 = {"name": "qjx", "school": {"school_name": "爱华小学", "class_name": "二年三班"}}
print("school" in dict1)

获取字段的值

dict1 = {"name": "qjx", "school": {"school_name": "爱华小学", "class_name": "二年三班"}}
print(dict1['school']['school_name'])  # 爱华小学
print(dict1.get('school', {}).get('school_name', {}))  # 爱华小学，键不存在返回{}

获取字段值（可设置默认值）

dict1 = {"name": "qjx"}
print(dict1.setdefault("name"))  # qjx
print(dict1.setdefault("age", 18))  # 18

循环字典键值对

dict1 = {"name": "qjx", "age": 18}
for key, value in dict1.items():
    print(f"{key}=>{value}")
    dict1[key] = "55"
print(dict1)  # {'name': '55', 'age': '55'}

循环字典的所有键或值

dict1 = {"name": "qjx", "age": 18}

# 遍历键
for i in dict1.keys():
    print(i)#name/age
# 遍历值
for i in dict1.values():
    print(i)#qjx/18

元组

元组合并

t1 = ('1', '2')
t2 = ('3',)

#第一种
t3 = t1 + t2
print(t3)# ('1', '2', '3')

#第二种
l3 = list(t3)
l3.append('4')
print(tuple(l3))#('1', '2', '3', '4')

根据值获取索引

a1 = (1,2,3)
print(a1.index(3))# 2

获取元素出现的次数

a1 = (1,2,3,3,3,3)
print(a1.count(3))# 4