一、函数定义
二、作用：提高代码的可重用性和可维护性（代码层次结构更清晰）。
三、函数返回值：
四、实例
# 定义根据月份，判断季节的方法．
def get_season(month):
if month < 1 or month > 12:
return "输入有误"
if month <= 3:
return "春天"
if month <= 6:
return "夏天"
if month <= 9:
return "秋天"
return "冬天"
print(get_season(5))
print(get_season(15))
# 练习：定义检查列表是否具有相同元素的方法
def is_repeating(list_target):
for r in range(len(list_target) - 1):
for c in range(r + 1, len(list_target)):
if list_target[r] == list_target[c]:
return True # 退出方法(可以退出两层循环)
return False
re01 = is_repeating([3,44,5])
re01 = is_repeating([3,44,5,44])
print(re01)
#练习：定义在控制台中显示直角三角形的函数
def print_triangle(height,char):
"""
打印三角型
:param height: 三角形高度
:param char: 组成三角型的字符
:return:
"""
for r in range(height):
for c in range(r+1):
print(char, end="")
print()
print_triangle(8,"*")
print_triangle(5,"#")
print_triangle(4,"?")
# 练习：定义在控制台中显示矩形的函数
def print_rect(r_count,c_count,char):
for r in range(r_count):# 0 1 2
for c in range(c_count):#01234 01234 01234
print(char,end = "") # 在一行输出
print() # 换行
print_rect(2,3,"*")
print_rect(5,2,"#")
# 参数:变量
# 函数调用者 告诉 函数定义者的信息
# 1. 参照下列代码，定义判断是否是奇数的方法．
# number = int(input("请输入整数:"))
# if number % 2 == 1:
# print("奇数")
# else:
# print("偶数")
def is_uneven(number):
# 方法１：传统方法
# if number % 2 == 1:
# return True
# else:
# return False
# 方法２：条件表达式
# return True if number % 2 == 1 else False
# 方法３：bool表达式
return number % 2 == 1
re = is_uneven(6)
print(re)
# 2.参照下列代码，定义根据月份返回天数的方法．
# 要求：考虑２月，如果是闰年返回２９天，否则返回２８天．
# month = int(input("请输入月份:"))
# if month < 1 or month > 12:
# print("输入有误")
# elif month == 2:
# print("28天")
# elif month == 4 or month == 6 or month == 9 or month == 11:
# print("30天")
# else:
# print("31天")
# 向外返回的结果return，其类型应该统一．
# 方法１：传统方法：
# def get_day_by_month(year,month):
# if month < 1 or month > 12:
# return 0
# elif month == 2:
# if year % 4 == 0 and year % 100 != 0 or year % 400 ==0:
# return 29
# else:
# return 28
# elif month == 4 or month == 6 or month == 9 or month == 11:
# return 30
# else:
# return 31
# 方法２：定义函数嵌套法+条件表达式精简代码
def is_leap_year(year):
return year % 4 == 0 and year % 100 != 0 or year % 400 == 0
def get_day_by_month(year, month):
if month < 1 or month > 12:
return 0
if month == 2:
return 29 if is_leap_year(year) else 28
if month in (4, 6, 9, 11):
return 30
return 31
day = get_day_by_month(2019,13)
print(day)
# 3.参照下列代码，定义获取最小值方法．
# min = list01[0]
# for i in range(1, len(list01)):
# # 发现更大的，则替换假设的．
# if min > list01[i]:
# min = list01[i]
# print(min)
def get_min(list_target):
min = list_target[0]
for i in range(1, len(list_target)):
if min > list_target[i]:
min = list_target[i]
return min
min = get_min([2, 3, 45, 1, 9, 3])
print(min)
# 4. 定义函数，判断字符串中存在的中文字符数量．
# 中文编码范围：0x4E00 ord(字符) 0x9FA5
def get_chinese_char_count(str_target):
count = 0
for item in str_target:
if 0x4E00 <= ord(item) <= 0x9FA5:
count += 1
return count
count = get_chinese_char_count("a你sid你f好ln")
print(count)
# 5. 扩展练习(定义函数，返回指定范围内的素数)
# 例如：１－－１００
# 方法１：传统方法
# def get_prime(bengin,end):
# list_prime = []
# for number in range(bengin,end+1):
# if number < 2:
# pass
# else:
# for i in range(2, number):
# if number % i == 0:
# break # 如果有结论了,就不需要在和后面的数字比较了
# else:
# list_prime.append(number)
# return list_prime
# 方法２：自定义函数相互之间嵌套法
def get_prime(bengin, end):
"""
生成指定范围内的所有素数
:param bengin: 开始
:param end: 结束
:return: 范围内的所有素数
"""
list_prime = []
for number in range(bengin, end + 1):
if is_prime(number):
list_prime.append(number)
return list_prime
def is_prime(number):
"""
判断是否为素数
:param number: 需要判断的数
:return: 是不是素数
"""
if number < 2:
return False # 不是素数
# 判断能否被中间的数字整除
for i in range(2, number):
if number % i == 0:
return False # 不是素数
return True # 是素数
primes = get_prime(5, 100)
print(primes)
primes = get_prime(-5, 50)
print(primes)
五、函数重构代码思想
案例：未重构前代码如下
shang_pin_info = {
101: {"name": "屠龙刀", "price": 10000},
102: {"name": "倚天剑", "price": 10000},
103: {"name": "九阴白骨爪", "price": 8000},
104: {"name": "九阳神功", "price": 9000},
105: {"name": "降龙十八掌", "price": 8000},
106: {"name": "乾坤大挪移", "price": 10000}
}
ding_dan = []
def gou_wu():
"""
购物
:return:
"""
while True:
item = input("1键购买，2键结算。")
if item == "1":
for key, value in shang_pin_info.items():
print("编号：%d，名称：%s，单价：%d。" % (key, value["name"], value["price"]))
while True:
cid = int(input("请输入商品编号："))
if cid in shang_pin_info:
break
else:
print("该商品不存在")
count = int(input("请输入购买数量："))
ding_dan.append({"cid": cid, "count": count})
print("添加到购物车。")
elif item == "2":
zong_jia = 0
for item in ding_dan:
shang_pin = shang_pin_info[item["cid"]]
print("商品：%s，单价：%d,数量:%d." % (shang_pin["name"], shang_pin["price"], item["count"]))
zong_jia += shang_pin["price"] * item["count"]
while True:
qian = float(input("总价%d元，请输入金额：" % zong_jia))
if qian >= zong_jia:
print("购买成功，找回：%d元。" % (qian - zong_jia))
ding_dan.clear()
break
else:
print("金额不足.")
gou_wu()
重构后代码如下：
dict_commodity_info = {
101: {"name": "屠龙刀", "price": 10000},
102: {"name": "倚天剑", "price": 10000},
103: {"name": "九阴白骨爪", "price": 8000},
104: {"name": "九阳神功", "price": 9000},
105: {"name": "降龙十八掌", "price": 8000},
106: {"name": "乾坤大挪移", "price": 10000}
}
list_order = []
def select_menu():
"""
菜单选择
"""
while True:
item = input("1键购买，2键结算。")
if item == "1":
buying()
elif item == "2":
settlement()
def settlement():
"""
结算
:return:
"""
print_order()
total_price = get_total_price()
pay(total_price)
def pay(total_price):
"""
支付
:param total_price: 需要支付的价格
:return:
"""
while True:
money = float(input("总价%d元，请输入金额：" % total_price))
if money >= total_price:
print("购买成功，找回：%d元。" % (money - total_price))
list_order.clear()
break
else:
print("金额不足.")
def print_order():
"""
打印订单
:return:
"""
for item in list_order:
commodity = dict_commodity_info[item["cid"]]
print("商品：%s，单价：%d,数量:%d." % (commodity["name"], commodity["price"], item["count"]))
def get_total_price():
"""
计算总价
:return:
"""
total_price = 0
for item in list_order:
commodity = dict_commodity_info[item["cid"]]
total_price += commodity["price"] * item["count"]
return total_price
def buying():
"""
购买
:return:
"""
print_commodity()
order = create_order()
list_order.append(order)
print("添加到购物车。")
def create_order():
"""
创建订单
:return:
"""
while True:
cid = int(input("请输入商品编号："))
if cid in dict_commodity_info:
break
else:
print("该商品不存在")
count = int(input("请输入购买数量："))
return {"cid": cid, "count": count}
def print_commodity():
"""
打印商品
:return:
"""
for key, value in dict_commodity_info.items():
print("编号：%d，名称：%s，单价：%d。" % (key, value["name"], value["price"]))
# 程序入口
select_menu()
注：虽然代码量变大了，但是在项目编程时，逻辑更清晰，维护更便捷
六、函数内存图示例（即可变／不可变类型在传参时的区别）：
示例1：
"""
内存图1.0
不可变对象传参
"""
def fun01(num01):
num01 = 2
print("num01:" + str(num01))# 2
number01 = 1
# 调用方法,在内存中开辟空间(栈帧)
# 栈帧中定义该方法内部创建的变量
# 方法执行完毕后，栈帧立即释放．
fun01(number01)
print("number01:" + str(number01))# 1
示例2：
"""
内存图2.0
可变对象传参
"""
def fun01(list_target):
list_target[0] = 2
print("list_target[0]:" + str(list_target[0]))
list_number = [1,2]
fun01(list_number)
print("list_number:" + str(list_number[0]))
示例3
def fun01(a,b,c):
a = 100
# 修改的是列表对象，
b[0] = 200
# 修改的是栈帧中的变量
c = 300
num01 = 1
list01 = [2]
list02 = [3]
fun01(num01,list01,list02)
print(num01)#? 1
print(list01)#? [２００]
print(list02)#? [３]
七、2048核心算法：
""" 2048 核心算法:降維 """ # 练习１：定义函数，将零元素移动到末尾 # [2,0,2,0] --> [2,2,0,0] # [0,2,2,0] --> [2,2,0,0] # [0,4,2,4] --> [4,2,4,0] """ 方案１ def zero_to_end(list_target): # １．将传入的列表中非零元素，拷贝到新列表中． # [2, 0, 2, 0] --> [2,2] --> [2,2,0,0] # [0, 4, 2, 4] -->[4, 2, 4] -->[4, 2, 4 ,0] # 2. 根据为零元素的数量，在新列表中添加零元素 # [2, 0, 2, 0] --> [2,2] new_list = [item for item in list_target if item != 0] # [2, 2] --> [2,2,0,0] new_list += [0] * list_target.count(0) # 3. 将新列表中元素赋值给传入的列表 list_target[:] = new_list """ # 方案2 def zero_to_end(list_target): # 从后往前判断，如果零元素，则删除，在末尾追加零元素 # [2, 0, 2, 0] --> [2, 2] --> [2, 2,0,0] for i in range(len(list_target) - 1, -1, -1): if list_target[i] == 0: del list_target[i] list_target.append(0) # list01 = [2, 0, 2, 0] # zero_to_end(list01) # print(list01) # 练习２：定义合并函数 # [2,2,0,0] --> [4,0,0,0] # [2,0,2,0] --> [4,0,0,0] # [2,0,0,2] --> [4,0,0,0] # [2,2,2,0] --> [4,2,0,0] def merge(list_target): # [2,0,2,0] --> [2,2,0,0] [2,2,2,0] zero_to_end(list_target) # [2,2,0,0] --> [4,0,0,0] [4,0,2,0] for i in range(len(list_target) -1): # 相邻且相同 if list_target[i] == list_target[i+1]: list_target[i] += list_target[i+1] list_target[i+1] = 0 zero_to_end(list_target)# [4,0,2,0] --> [4,2,0,0] # list01 = [2,2,2,0] # merge(list01) # print(list01) # 练习３：将二维列表，以表格的格式显示在控制台中 list01 = [ [2,0,0,2], [2,2,0,0], [2,0,4,4], [4,0,0,2], ] def print_map(map): for r in range(len(map)): for c in range(len(map[r])): print(map[r][c],end = " ") print() # print_map(list01) #练习４：定义向左移动函数．１１：５０ """ [2,0,0,2] [4,0,0,0] [2,2,0,0] [4,0,0,0] [2,0,4,4] [2,8,0,0] [4,0,0,2] [4,2,0,0] """ def move_left(map): # 获取第行 for r in range(len(map)): # 从左往右获取行 # 交给merge进行合并 merge(map[r]) def move_right(map): # 获取第行 for r in range(len(map)): # 从右往左获取行 # 交给merge进行合并 list_merge = map[r][::-1] merge(list_merge) map[r][::-1] = list_merge # 作业１：定义向上移动函数 # 从上往下获取列 # 交给合并方法 # 还给原列 # 作业２：定义向下移动函数 # 从下往上获取列 # 交给合并方法 # 还给原列 def move_up(list_target): list_merge = [] for c in range(len(list_target[0])): for r in range(len(list_target)): list_merge.append(list_target[r][c]) merge(list_merge) for r in range(len(list_target)): list_target[r][c] = list_merge[r] list_merge = [] def move_down(list_target): list_merge = [] for c in range(len(list_target[0])): for r in range(len(list_target) - 1, -1, -1): list_merge.append(list_target[r][c]) merge(list_merge) for r in range(len(list_target)): list_target[r][c] = list_merge[3 - r] list_merge = [] # move_left(list01) # move_right(list01) # move_up(list01) move_down(list01) print_map(list01)