Python学习:基础(5)

[0]内置的那些函数,可以通过help或者https://docs.python.org/3/library/进行查阅.

[1]对进制的转换,10进制整数到2，8，16,bin(),oct(),hex()就可以转换到相应的进制了.

[2]各个进制到10进制的转换,int(obxxxxx),int(ox…..)或者int(‘xxxxxxxxxx’,2),int(‘xxxxxxxx’,8)

以下代码作为练习求解任意m进制到n进制的转换,作为一种良好的习惯,我们应该检查所有可能的输入,m,n必须是整数,要处理的数也应该是整数(但是不一定是正数),m如果不是数,调用int将会出错,如何判断一个字符串是否是数?这里需要用到正则表达式,以后再处理.

m = int(input('please input the orginal number system'))
n = int(input('please input the objective number system'))
m_str = input('the orginal integer ')

if(float(m_str)==int(float(m_str))):
        m_number = int(m_str,m)#get the numeric value of m
        symbol = ''

        if(m_number<0):#figure out the final symbol
                m_number = abs(m_number)#get positive value
                symbol = '-'

        if(n == 10):# m convert to 10
                print(symbol+str(m_number))
        else:#10 convert to n
                ans = ''
                while(m_number):
                        ans = str(m_number%n) + ans#doing the mod
                        m_number = m_number//n#warning!!: using // not /
                print(symbol+ans)#print the answer
else:
        print('input is not integer')

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学会定义函数:def：,返回值(多个返回值实际上是一个tuple),参数检查。求一元二次方程解的代码.

import math
def quadratic(a, b, c):
    if(not(isinstance(a,(int,float))and isinstance(b,(int,float)) and isinstance(c,(int,float)))):#check the argument type
        print('the a,b,c is typerror')
        return
    if(b*b>=4*a*c):
        r = math.sqrt(b*b-4*a*c)
        return (-b+r)/(2*a),(-b-r)/(2*a)
    else:
        print('there is not real root')
        return

print(quadratic(2, 3, 1))
print(quadratic(1, 3, -4))
print(quadratic(1, -2, 1))
print(quadratic(5, 1, 3))
print(quadratic('1', 3, -4))