廖雪峰老师Python3教程练习整理

1.定义一个函数quadratic(a, b, c)，接收3个参数，返回一元二次方程：ax2 + bx + c = 0的两个解

# -*- coding: utf-8 -*-
import math
def quadratic(a, b, c):
    if not isinstance(a,(int,float)):
        raise TypeError('bad operand type')
    if b==0&a==0:
        return '参数a,b不能同时为0'
    if b*b-4*a*c<0:
        return '该方程无解'
    elif b*b-4*a*c==0:
        if a==0:
            x=-(b/c)
            return x
        elif a!=0:
            x=-b/(2*a)
            return x
    elif b*b-4*a*c>0:
        x=(-b+math.sqrt(b*b-4*a*c))/(2*a)
        y=(-b-math.sqrt(b*b-4*a*c))/(2*a)
        return x,y
 
# 测试:
print('quadratic(2, 3, 1) =', quadratic(2, 3, 1))
print('quadratic(1, 3, -4) =', quadratic(1, 3, -4))
 
if quadratic(2, 3, 1) != (-0.5, -1.0):
    print('测试失败')
elif quadratic(1, 3, -4) != (1.0, -4.0):
    print('测试失败')
else:
    print('测试成功')
2.去除字符串首尾的空格

# -*- coding: utf-8 -*-
def trim(s):
    while s[:1] == ' ':
        s = s[1:]
    while s[-1:] == ' ':
        s = s[:-1]
    return s
if trim('hello   ') != 'hello':
    print('失败')
else:
    print('成功')
<2>

# -*- coding: utf-8 -*-
def trim(s):
    while len(s) > 0 and s[0] == ' ':
        s = s[1:]
    while len(s) > 0 and s[-1] == ' ':
        s = s[:-1]
    return s
if trim('hello   ') != 'hello':
    print('失败')
else:
    print('成功')