print("-------------输出语句-------------"); message="Hello Python world"; print(message); print("-------------首字母大写-------------"); name="ada lovelace"; print(name.title()); print("-------------大小写-------------"); print(name.upper()); print(name.lower()); print("-------------拼接字符串-------------"); first_name = "ada" last_name = "lovelace" full_name = first_name + " " + last_name print(full_name); print("-------------添加空白-------------"); print("\tPython"); print("Languages:\nPython\nC\nJavaScript"); print("-------------删除空白-------------"); print("Hello ".rstrip()); print("-------------运算-------------"); print(2+3); print(3-2); print(2*3); print(3/2); print(3**2); print(3**3); print(10**6); print(0.1+0.1); print(0.2+0.2); print("------------注释-------------"); # 测试注释
-------------输出语句------------- Hello Python world -------------首字母大写------------- Ada Lovelace -------------大小写------------- ADA LOVELACE ada lovelace -------------拼接字符串------------- ada lovelace -------------添加空白------------- Python Languages: Python C JavaScript -------------删除空白------------- Hello -------------运算------------- 5 1 6 1.5 9 27 1000000 0.2 0.4 ------------注释------------- Process finished with exit code 0
print("-------------列表-------------"); bicycles = ['trek', 'cannondale', 'redline', 'specialized']; print(bicycles); print("-------------访问列表元素-------------"); print(bicycles[0]); print("-------------修改列表元素-------------"); bicycles[0]='ducati'; print(bicycles); print("-------------添加列表元素-------------"); bicycles.append('test'); print(bicycles); print("-------------插入列表元素-------------"); bicycles.insert(0,'test2'); print(bicycles); print("-------------删除列表元素-------------"); del bicycles[0]; print(bicycles); print(bicycles.pop()); print(bicycles); print("-------------排序列表元素-------------"); bicycles.sort(); print(bicycles); print("-------------倒叙打印列表元素-------------"); print(bicycles.reverse()); print("-------------列表长度-------------"); print(len(bicycles)); print("-------------数值列表------------"); numbers=list(range(1,6)); print(numbers);
-------------列表------------- ['trek', 'cannondale', 'redline', 'specialized'] -------------访问列表元素------------- trek -------------修改列表元素------------- ['ducati', 'cannondale', 'redline', 'specialized'] -------------添加列表元素------------- ['ducati', 'cannondale', 'redline', 'specialized', 'test'] -------------插入列表元素------------- ['test2', 'ducati', 'cannondale', 'redline', 'specialized', 'test'] -------------删除列表元素------------- ['ducati', 'cannondale', 'redline', 'specialized', 'test'] test ['ducati', 'cannondale', 'redline', 'specialized'] Process finished with exit code 0
print("-------------检查是否相等-------------"); car='bmw'; print(car=='bmw'); print(car=='audi'); print(car=='BMW'); print(car.upper()=='BMW'); age=18; print(age==18); print(age>=18); print(age<=18); print(age>18); print(age<18); age_0 = 22; age_1 = 18; print(age_0 >= 21 and age_1 >= 21); print(age_0 >= 21 or age_1 >= 21); print("-------------if语句-------------"); age = 19 if age >= 18: print("You are old enough to vote!"); age=17 if age>=18: print("You are old enough to vote!"); else: print("Sorry you are too young"); age = 12 if age < 4: print("Your admission cost is $0.") elif age < 18: print("Your admission cost is $5.") else: print("Your admission cost is $10.") age = 12 if age < 4: price = 0 elif age < 18: price = 5 elif age < 65: price = 10 elif age >= 65: price = 5 print("Your admission cost is $" + str(price) + ".")
-------------检查是否相等------------- True False False True True True True False False False True -------------if语句------------- You are old enough to vote! Sorry you are too young Your admission cost is $5. Your admission cost is $5. Process finished with exit code 0
print("-------------一个简单的字典-------------"); alien_0 = {'color': 'green', 'points': 5} print(alien_0['color']) print(alien_0['points']) print("-------------访问字典中的值------------"); alien_0={'color':'green'}; print(alien_0['color']); print("-------------先创建一个空字典------------"); alien_0 = {} alien_0['color'] = 'green' alien_0['points'] = 5 print(alien_0) print("-------------修改字典中的值------------"); alien_0={'color':'green'} print("The alien is " + alien_0['color'] + ".") alien_0['color'] = 'yellow' print("The alien is now " + alien_0['color'] + ".") print("-------------删除键值对------------"); alien_0 = {'color': 'green', 'points': 5} print(alien_0); del alien_0['points'] print(alien_0); print("-------------遍历字典------------"); user_0 = { 'username': 'efermi', 'first': 'enrico', 'last': 'fermi', } for key,value in user_0.items(): print("\nKey:"+key) print("Value:"+value)
-------------一个简单的字典------------- green 5 -------------访问字典中的值------------ green -------------先创建一个空字典------------ {'color': 'green', 'points': 5} -------------修改字典中的值------------ The alien is green. The alien is now yellow. -------------删除键值对------------ {'color': 'green', 'points': 5} {'color': 'green'} -------------遍历字典------------ Key:username Value:efermi Key:first Value:enrico Key:last Value:fermi Process finished with exit code 0
print("-------------函数input()的工作原理-------------"); message = input("Tell me something, and I will repeat it back to you: ") print(message) print("-------------编写清晰的程序-------------"); name=input("Please enter your name:"); print("Hello,"+name+"!"); print("-------------求模运算符-------------"); print(4%3); print("-------------while循环-------------"); current_number = 1 while current_number <= 5: print(current_number) current_number += 1 print("-------------让用户选择何时退出-------------"); prompt = "\nTell me something, and I will repeat it back to you:" prompt += "\nEnter 'quit' to end the program. " message = "" while message != 'quit': message = input(prompt) print(message) print("-------------break语句-------------"); prompt = "\nPlease enter the name of a city you have visited:" prompt += "\n(Enter 'quit' when you are finished.) " while True: city = input(prompt) if city == 'quit': break else: print("I'd love to go to " + city.title() + "!")
-------------函数input()的工作原理------------- Tell me something, and I will repeat it back to you: Hello World Hello World -------------编写清晰的程序------------- Please enter your name:Alice Hello,Alice! -------------求模运算符------------- 1 -------------while循环------------- 1 2 3 4 5 -------------让用户选择何时退出------------- Tell me something, and I will repeat it back to you: Enter 'quit' to end the program. Hello World Hello World Tell me something, and I will repeat it back to you: Enter 'quit' to end the program. quit quit -------------break语句------------- Please enter the name of a city you have visited: (Enter 'quit' when you are finished.) ShangHai I'd love to go to Shanghai! Please enter the name of a city you have visited: (Enter 'quit' when you are finished.) quit Process finished with exit code 0
print("-------------函数-------------"); def greet_user(): print("Hello World") print("-------------区分线-------------"); greet_user(); print("-------------调用函数-------------"); def tpl_sum( T ): #定义函数tpl_sum() result = 0 #定义result的初始值为0 for i in T: #遍历T中的每一个元素i result += i #计算各个元素i的和 return result #函数tpl_sum()最终返回计算的和 print("(1,2,3,4)元组中元素的和为:",tpl_sum((1,2, 3,4))) #使用函数tpl_sum()计算元组内元素的和 print("[3,4,5,6]列表中元素的和为:",tpl_sum([3,4, 5,6])) #使用函数tpl_sum()计算列表内元素的和 print("[2.7,2,5.8]列表中元素的和为:",tpl_sum([2.7, 2,5.8])) #使用函数tpl_sum()计算列表内元素的和 print("[1,2,2.4]列表中元素的和为:",tpl_sum([1,2,2.4])) #使用函数tpl_sum()计算列表内元素的和
-------------函数------------- -------------区分线------------- Hello World -------------调用函数------------- (1,2,3,4)元组中元素的和为: 10 [3,4,5,6]列表中元素的和为: 18 [2.7,2,5.8]列表中元素的和为: 10.5 [1,2,2.4]列表中元素的和为: 5.4 Process finished with exit code 0
def<函数名>(参数列表): <函数语句> return<返回值>
在上述格式中,参数列表和返回值不是必需的,return 后也可以不跟返回值,甚至连 return 也没有。如果 return 后没有返回值,并且没有 return 语句,这样的函数都会返回 None 值。有些函数可能既不需要传递参数,也没有返回值。
注意:当函数没有参数时,包含参数的圆括号也必须写上,圆括号后也必须有“:”。
在 Python 程序中,完整的函数是由函数名、参数以及函数实现语句(函数体)组成的。在函数声明中,也要使用缩进以表示语句属于函数体。如果函数有返回值,那么需要在函数中使用 return 语句返回计算结果。
根据前面的学习,可以总结出定义 Python 函数的语法规则,具体说明如下所示。
print("-------------类-------------"); class MyClass: #定义类MyClass "这是一个类." myclass = MyClass() #实例化类MyClass print('输出类的说明:') #显示文本信息 print(myclass.__doc__) #显示属性值 print('显示类帮助信息:') help(myclass) print("-------------类对象-------------"); class MyClass: #定义类MyClass """一个简单的类实例""" i = 12345 #设置变量i的初始值 def f(self): #定义类方法f() return 'hello world' #显示文本 x = MyClass() #实例化类 #下面两行代码分别访问类的属性和方法 print("类MyClass中的属性i为:", x.i) print("类MyClass中的方法f输出为:", x.f()) print("-------------构造方法-------------"); class Dog(): """小狗狗""" def __init__(self, name, age): """初始化属性name和age.""" self.name = name self.age = age def wang(self): """模拟狗狗汪汪叫.""" print(self.name.title() + " 汪汪") def shen(self): """模拟狗狗伸舌头.""" print(self.name.title() + " 伸舌头") print("-------------调用方法-------------"); def diao(x,y): return (abs(x),abs(y)) class Ant: def __init__(self,x=0,y=0): self.x = x self.y = y self.d_point() def yi(self,x,y): x,y = diao(x,y) self.e_point(x,y) self.d_point() def e_point(self,x,y): self.x += x self.y += y def d_point(self): print("亲,当前的位置是:(%d,%d)" % (self.x,self.y)) ant_a = Ant() ant_a.yi(2,7) ant_a.yi(-5,6)
-------------类------------- 输出类的说明: 这是一个类. 显示类帮助信息: Help on MyClass in module __main__ object: class MyClass(builtins.object) | 这是一个类. | | Data descriptors defined here: | | __dict__ | dictionary for instance variables (if defined) | | __weakref__ | list of weak references to the object (if defined) -------------类对象------------- 类MyClass中的属性i为: 12345 类MyClass中的方法f输出为: hello world -------------构造方法------------- -------------调用方法------------- 亲,当前的位置是:(0,0) 亲,当前的位置是:(2,7) 亲,当前的位置是:(7,13) Process finished with exit code 0