廖雪峰python教程学习之习题解析
第一天
条件判断练习测试
# 小明身高1.75，体重80.5kg。请根据BMI公式（体重除以身高的平方）帮小明计算他的BMI指数，并根据BMI指数：
# 低于18.5：过轻
# 18.5-25：正常
# 25-28：过重
# 28-32：肥胖
# 高于32：严重肥胖
# 用if-elif判断并打印结果：
def exp_if():
height = 1.75
weight = 80.5
bmi = weight/(height*height)
if bmi<18.5:
print("you BMI is {}".format(bmi))
elif bmi<=25:
print("you BMI is {},正常".format(bmi))
elif bmi<=28:
print("you BMI is {},过重".format(bmi))
elif bmi<=32:
print("you BMI is {},肥胖".format(bmi))
else:
print("you BMI is \t{:.3f},严重肥胖".format(bmi))
if __name__ == '__main__':
exp_if()利用列表或者元组实现循环
names = ['Michael', 'Bob', 'Tracy']
for name in names:
print(name)
sum = 0
for x in [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]:
sum = sum + x
print(sum)
##实现计算0+1+2++100
sum=0
for i in range(101):
sum=sum+i
print(sum)计算100以内所有奇数之和
#法一：
sum=0
for i in range(1,100,2):
sum=sum+i
print (sum)
#法二：
sum=0
i=1
while i<101 :
sum=sum+i
i=i+2
print(sum)标准化输出格式打印练习
#请利用循环依次对list中的每个名字打印出Hello, xxx!：
L = ['Bart', 'Lisa', 'Adam']
len=len(L)
for i in range(len):
print("Hello {}".format(L[i]))利用.format{}实现标准化输出格式定义
print "{:.2f}".format(3.1415926) #3.14,保留小数点后两位
print "{:+.2f}".format(3.1415926) #+3.14 带符号保留小数点后两位
print "{:+.2f}".format(-10) #-10.00 带符号保留小数点后两位
print "{:+.0f}".format(-10.00) #-10 不带小数
print "{:0>2d}".format(1) #01 数字补零 (填充左边, 宽度为2)
print "{:x<2d}".format(1) #1x 数字补x (填充右边, 宽度为4)
print "{:x<4d}".format(10) #10xx 数字补x (填充右边, 宽度为4)
print "{:,}".format(1000000) #1,000,000 以逗号分隔的数字格式
print "{:.2%}".format(0.12) #12.00% 百分比格式
print "{:.2e}".format(1000000) #1.00e+06 指数记法
print "{:<10d}".format(10) #10 左对齐 (宽度为10)
print "{:>10d}".format(10) # 10 右对齐 (默认, 宽度为10)
print "{:^10d}".format(10) # 10 中间对齐 (宽度为10)字典使用
d = {'Michael': 95, 'Bob': 75, 'Tracy': 85}
判断是否在字典中
def test_dict():
SC={"Anan":"90","Ping":"88","Ling":"83"}
print(SC['Ping'])
print(SC.get('Ping'))
if __name__ == '__main__':
test_dict()实现输入一个name 如果在列表中 输出得分 判断得分等级 如果没有输出该名字不在名单内
def scoretest(score):
if score>90:
achievement ='优秀'
elif score>=80:
achievement ='良好'
elif score >60:
achievement='及格'
else:
achievement='不及格'
return achievement
if __name__ == '__main__':
input_name=input("Please input you name:")
dict_name_and_score={"Anan":"90","Ping":"88","Ling":"55"}
if input_name in dict_name_and_score:
print('{} score is {} belong to {}'.format(input_name,dict_name_and_score[input_name],scoretest(int(dict_name_and_score[input_name]))))
else:
print("{} is not in our Name list".format(input_name))实现计算园面积s=πr*r
import math
import numpy
def Circular_Area(r):
PI=3.14
s=PI*numpy.square(r)
return(s)
if __name__ == '__main__':
input=input("R is :")
print("The circular area with a radius of {} is:{:.2f}".format(input,Circular_Area(int(input))))
函数quadratic(a, b, c)，接收3个参数，返回一元二次方程：ax2 + bx + c = 0
import numpy as np
def quadratic(a,b,c):
x1=(-b+np.sqrt(b*b-4*a*c))/(2*a)
x2=(-b-np.sqrt(b*b-4*a*c))/(2*a)
return(x1,x2)
def main():
quadratic(1,3,-4)
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')
if __name__ == '__main__':
main()https://www.liaoxuefeng.com/wiki/0014316089557264a6b348958f449949df42a6d3a2e542c000/001431756044276a15558a759ec43de8e30eb0ed169fb11000
第二天
切片
L=[]
n=1
while n<99:
L.append(n)
n=n+2
print(L)#取list或者元组的前三个元素
# def test_list():
# L=[]
# n=1
# while n<=99:
# L.append(n)
# n=n+2
# # print(L)
# print(L[:3])
# # return L
# pass
# def test_tuple():
# T=('Anan','Ping','Ling','Zhen')
# # return T
# print(T[:3])
# print(T[::2]) #开始 结束 步长
# if __name__ == '__main__':
# # test_list()
# test_tuple()列表生成式训练
L1 = ['Hello', 'World', 18, 'Apple', None]
L2=[]
j=0
for i in range(len(L1)-1):
if isinstance(L1[i],str):
L2.append(L1[i].lower())
j=j+1
if L2 == ['hello', 'world', 'apple']:
print('测试通过!')
else:
print('测试失败!')https://www.liaoxuefeng.com/wiki/0014316089557264a6b348958f449949df42a6d3a2e542c000/0014317852443934a86aa5bb5ea47fbbd5f35282b331335000
第三天
高阶函数
def add(x, y, f):
return f(x) + f(y)
print(add(-5, 6, abs))def add(x,y,f):
return f(x)+f(y)
def min(x,y,h):
return(h(x)-h(y))
def h(z):
return abs(z)
if __name__ == '__main__':
x=-5
y=6
f=abs
# print(add(h(3),h(2)))
print(min(h(3),h(2),h))
print(min(3,4,h))map reduace的实现
>map()函数接收两个参数 一个是函数 一个是Iterable,map将传入的函数依次作用到序列的每个元素，并把结果作为Iterator返回
#!/usr/bin/env python
# -*- coding: utf-8 -*-
#function (1) 利用map计算一个列表中数的平方 (2)利用reduace函数把序列[1, 3, 5, 7, 9]变换成整数13579
from functools import reduce
def f(x):
return x*x
def map_test():
r=map(f,[1, 2, 3, 4, 5, 6, 7, 8, 9])
print(list(r))
print(list(map(str,[1,2,3,3,45,5,5,4])))
def fn(x,y):
return x*10+y
def reduace_test():
print(reduce(fn,[1,2,5,6]))
pass
if __name__ == '__main__':
# map_test()
reduace_test()结合MapReduace实现将字符转化为数字进行运算
#!/usr/bin/env python
# -*- coding: utf-8 -*-
#function 结合MapReduace实现将字符转化为数字进行运算
from functools import reduce
def fn(x,y):
return x*10+y
def char2num(s):
digits={'0':0,'1':1,'2':2,'3':3,'4':4,'5':5,'6':6,'7':7,'8':8,'9':9}
return digits[s]
print(reduce(fn,map(char2num,'1456')))利用map()函数，把用户输入的不规范的英文名字，变为首字母大写，其他小写的规范名字。
# -*- coding: utf-8 -*-
def normalize(name):
name.title()
# 测试:
##输入：['adam', 'LISA', 'barT']，输出：['Adam', 'Lisa', 'Bart']：
L1 = ['adam', 'LISA', 'barT']
L2 = list(map(normalize, L1))
print(L2)利用prod()函数实现可以接受一个list并利用reduce()求积：
from functools import reduce
def prod(L):
sumL=1
for i in range(len(L)):
sumL=sumL*L[i]
return sumL
print('3 * 5 * 7 * 9 =', prod([3, 5, 7, 9]))
if prod([3, 5, 7, 9]) == 945:
print('测试成功!')
else:
print('测试失败!')from functools import reduce
def prod(x,y):
return x*y
result = reduce(prod,[3,5,7,9])
print(result)把字符串’123.456’转换成浮点数123.456
def str2float(s):
return float(s)
print('str2float(\'123.456\') =', str2float('123.456'))
if abs(str2float('123.456') - 123.456) < 0.00001:
print('测试成功!')
else:
print('测试失败!')利用filter()筛选出回数
def is_palindrome(n):
return str(n)==str(n)[::-1]
# 测试:
output = filter(is_palindrome, range(1, 1000))
print('1~1000:', list(output))
if list(filter(is_palindrome, range(1, 200))) == [1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 22, 33, 44, 55, 66, 77, 88, 99, 101, 111, 121, 131, 141, 151, 161, 171, 181, 191]:
print('测试成功!')
else:
print('测试失败!')L = [('Bob', 75), ('Adam', 92), ('Bart', 66), ('Lisa', 88)]
def by_name(t):
return t[0]
def by_score(t):
return t[1]
L2 = sorted(L, key=by_score)
print(L2)匿名函数
关键字lambda表示匿名函数，冒号前面的x表示函数参数。
L=list(filter(lambda n :n%2==1,range(1,20)))
print(L)
def is_odd(n):
return n % 2 == 1
L1 = list(filter(is_odd, range(1, 20)))
print(L1)
def is_odd2(n):
return lambda n:n%2==1
L2 = list(filter(is_odd2(0), range(1, 20)))
print(L2)python内建函数：https://docs.python.org/3/library/functions.html
第四天
实现面相对象编程
# !/usr/bin/env python
# -*- coding: utf-8 -*-
'实现面相对象编程'
class Student(object):
"""docstring for Student"""
def __init__(self, name,score):
self.name=name
self.score=score
def print_score(self):
return '%s,%s'%(self.name,self.score)
def get_grade(self):
if self.score>=90:
return 'A'
elif self.score>=80:
return 'B'
elif self.score>=60:
return 'C'
else:
return 'D'
def main():
anan=Student('Anan',88)
anan.print_score()
print(anan.name,anan.score,anan.get_grade())
if __name__ == '__main__':
main()'定义私有变量(private)'
class Student(object):
def __init__(self, name,score):
self.__name=name
self.__score=score
def print_score(self):
return '%s,%s'%(self.__name,self.__score)
def get_name(self):
return self.__name
def get_score(self):
return self.__score
def main():
anan=Student('Anan',88)
print(anan.get_name(),anan.get_score())
if __name__ == '__main__':
main()'访问限制训练'
class Student(object):
def __init__(self, name, gender):
self.name = name
self.__gender = gender
def get_gender(self):
return self.__gender
def set_gender(self,gender):
self.__gender=gender
return self.__gender
def test():
bart = Student('Bart', 'male')
if bart.get_gender() != 'male':
print('测试失败!')
else:
bart.set_gender('female')
if bart.get_gender() != 'female':
print('测试失败!')
else:
print('测试成功!')
if __name__ == '__main__':
test()继承和多态
#!/usr/bin/env python3
# -*- coding: utf-8 -*-
class Animal(object):
def run(self):
print('Animal is running...')
class Dog(Animal):
def run(self):
print('Dog is running...')
class Cat(Animal):
def run(self):
print('Cat is running...')
def run_twice(animal):
animal.run()
animal.run()
a = Animal()
d = Dog()
c = Cat()
print('a is Animal?', isinstance(a, Animal))
print('a is Dog?', isinstance(a, Dog))
print('a is Cat?', isinstance(a, Cat))
print('d is Animal?', isinstance(d, Animal))
print('d is Dog?', isinstance(d, Dog))
print('d is Cat?', isinstance(d, Cat))
run_twice(c)为了统计学生人数，可以给Student类增加一个类属性，每创建一个实例，该属性自动增加：
class Student(object):
count = 0
def __init__(self, name):
self.name = name
Student.count+=1
# 测试:
if Student.count != 0:
print('测试失败!')
else:
bart = Student('Bart')
if Student.count != 1:
print('测试失败!')
else:
lisa = Student('Bart')
if Student.count != 2:
print('测试失败!')
else:
print('Students:', Student.count)
print('测试通过!')使用slots
使用slots可以限制实例的属性，只允许对类的实例添加slots定义的属性
slots不能限制继承类的实例属性。如果被继承的类也需要进行限定需要子类也添加slots的限定
使用@property
IO编程
python读取文件：
'方法一'
f=open('filename','r')
f.read()
f.close()
'方法二'#-->推荐
with open('filename','r') as f:
f.read()
python写入文件：
'方法一'
f=open('filename','w')
f.write()
f.close()
'方法二'#-->推荐
with open('filename','w') as f:
f.write('输入你需要写入的内容')
方法三：
file=r'filename'
with open(file,'w+') as f:
f.write('输入你需要写入的内容')
输入输出参数详解：
‘r’：读\
‘w’：写\
‘a’：追加\
‘r+’ == r+w（可读可写，文件若不存在就报错(IOError)）\
‘w+’ == w+r（可读可写，文件若不存在就创建）\
‘a+’ ==a+r（可追加可写，文件若不存在就创建）\
对应的，如果是二进制文件，就都加一个b：\
‘rb’ ‘wb’ ‘ab’ ‘rb+’ ‘wb+’ ‘ab+’
正则表达式
\d匹配一个数字\
\w匹配一个字母或数字\
*表示任意个字符（包括0个)\
+表示至少一个字符\
?表示0个或1个字符\
{n}表示n个字符\
{n,m}表示n-m个字符\
A|B可以匹配A或B\
^表示行的开头\
^\d表示必须以数字开头\
表示行的结束 \d 表 示 行 的 结 束 \d 表示必须以数字结束
案例：正则匹配邮箱
test='[email protected]'
if re.match(r'^[0-9a-zA-Z_.]+@[a-z]+.com$', test):
print('ok')
else:
print('failed')装饰器
#!/usr/bin/env python
# -*- coding: utf-8 -*-
def aa(func):
def bb():
print("abc")
result=func()
return bb
@aa
def main():
print("main")
if __name__ == '__main__':
main()未完待续…