【RUNOOB】python学习之python3实例以及知识点解析

1.python数字求和

#!/usr/bin/python3

num1=input('input first number:')
num2=input('input second number:')

sum=float(num1) + float(num2)
print('number {0} + number {1} is {2}').format(num1,num2,sum)

1.1 读取输入

https://www.runoob.com/python3/python3-inputoutput.html

(1) input内置函数用于读取用户输入;

1.2 类型转换(显式类型转换与隐式类型转换)

https://www.runoob.com/python3/python3-type-conversion.html

(1) 隐式类型转换中,python自动将一种数据类型转换为另外一种数据类型,不需要用户干预;

(2) 显式类型转换需要使用int(), float(), str()等预定义函数;

1.3 str.format()函数格式化输出

https://www.runoob.com/python3/python3-inputoutput.html

2.python平方根

#!/usr/bin/python3

num = float(input('请输入一个数字： '))
num_sqrt = num ** 0.5
print(' %0.3f 的平方根为 %0.3f'%(num ,num_sqrt))

2.1 旧式字符串格式化

https://www.runoob.com/python3/python3-inputoutput.html

#!/usr/bin/python3
import cmath
 
num = int(input("请输入一个数字: "))
num_sqrt = cmath.sqrt(num)
print('{0} 的平方根为 {1:0.3f}+{2:0.3f}j'.format(num ,num_sqrt.real,num_sqrt.imag))

2.2 模块的使用以及math与cmatch模块的对比

https://www.runoob.com/python3/python3-module.html

https://www.runoob.com/w3cnote/python-math-and-cmath-module.html

3.计算圆的面积

3.1 函数与函数调用

https://www.runoob.com/python3/python3-function.html

#!/usr/bin/python3

def findArea(r):
    PI = 3.142
    return PI * (r*r)
 
# 调用方法
print("圆的面积为 %.6f" % findArea(5))

4.python交换变量(使用临时变量或不使用临时变量)

4.1 不使用临时变量的变量交换

#!/usr/bin/python3
x = input('输入 x 值: ')
y = input('输入 y 值: ')
 
# 不使用临时变量
x,y = y,x
 
print('交换后 x 的值为: {}'.format(x))
print('交换后 y 的值为: {}'.format(y))

5.python if与内嵌if

https://www.runoob.com/python3/python3-conditional-statements.html

#!/usr/bin/python3

num = float(input("输入一个数字: "))
if num > 0:
   print("正数")
elif num == 0:
   print("零")
else:
   print("负数")


num = float(input("输入一个数字: "))
if num >= 0:
   if num == 0:
       print("零")
   else:
       print("正数")
else:
   print("负数")

6.python判断字符串是否为数字

(1) python float函数(),异常处理try/except语句,pass语句

https://www.runoob.com/python/python-func-float.html

https://www.runoob.com/python/python-exceptions.html

https://www.runoob.com/python/python-pass-statement.html

#!/usr/bin/python3
def is_number(s):
    try:
        float(s)
        return True
    except ValueError:
        pass
 
    try:
        import unicodedata
        unicodedata.numeric(s)
        return True
    except (TypeError, ValueError):
        pass
 
    return False

7.python获取最大值函数

(1) python max()函数;

https://www.runoob.com/python/func-number-max.html

#!/usr/bin/python3
print(max(1, 2))
print(max('a', 'b'))
 
# 也可以对列表和元组使用
print(max([1,2]))
print(max((1,2)))
 
# 更多实例
print("80, 100, 1000 最大值为: ", max(80, 100, 1000))
print("-20, 100, 400最大值为: ", max(-20, 100, 400))
print("-80, -20, -10最大值为: ", max(-80, -20, -10))
print("0, 100, -400最大值为:", max(0, 100, -400))

8.python质数判断

(1) python range()函数, 运算符, 循环语句for/else结构;

https://www.runoob.com/python/python-func-range.html

https://www.runoob.com/python3/python3-basic-operators.html

https://www.runoob.com/python3/python3-loop.html

#!/usr/bin/python3
num = int(input("请输入一个数字: "))
 
# 质数大于 1
if num > 1:
   # 查看因子
   for i in range(2,num):
       if (num % i) == 0:
           print(num,"不是质数")
           print(i,"乘于",num//i,"是",num)
           break
   else:
       print(num,"是质数")
       
# 如果输入的数字小于或等于 1，不是质数
else:
   print(num,"不是质数")

9.python输出指定范围内的素数

(1) 循环中的else子句(如for...else)-只有当循环正常结束时,才会执行的else子句;如果循环中执行了break语句,那么循环中的else子句将不会执行;

#!/usr/bin/python3

lower =int(input("min value of a range:"))
upper=int(input("max value of a range:"))

for num in range(lower, upper+1)
    if num>1:
        for i in range(2,num):
            if (num%i)==0:
                break
        else:
            print(num)

10.python阶乘实例

#!/usr/bin/python3

num=int(input("pls input a number:"))

factorial=1

if num<0:
    print("you shoule input a number that is larger than 0")
elif num==0:
    print("0!=1")
else:
    for i in range(1,num+1):
        factorial=factorial*i
    print("(%d)! is %d"%(num,factorial))