1小时学会Python-深度学习原理与实现的1.4节

type(2)

type(3.14)

print(2,3.14,"http://hwdong.net",True)
print(type(2),type(3.14),type("http://hwdong.net"),type(False))

print('''http://hwdong.net is
         a blog teaching computer programming''')

id(10)

blog = "hwdong-net.github.io"
print(blog)
blog = "http://"+blog
print(blog)

a = 3.14              #a是对象3.14的引用
b = a                 #b和a引用同一个对象3.14
a = "hwdong-net.github.io"      #a引用了新的字符串对象"hwdong.net"
print(a)
print(b)

a = int(3.14)
print(a)
print(type(a))
b= float("3.14")
print(b)
print(type(b))

score = input("请输入一个学生的分数：")
print(score)

x = 15
y = 2
print('x + y =',x+y)
print('x - y =',x-y)
print('x * y =',x*y)
print('x / y =',x/y)
print('x // y =',x//y)
print('x ** y =',x**y)
print('x % y =',x%y)

print("http:"+"//"+"hwdong.net") 
print("hello "*3)

print("hello "*"world")

x = 15
y = 2
print('x > y is',x>y)
print('x < y is',x<y)
print('x == y is',x==y)
print('x != y is',x!=y)
print('x >= y is',x>=y)
print('x <= y is',x<=y)

print(not 0)
print(not "")           
print(not False)
print(not 2)
print(not "hwdong")          

print(3 or 2)      #因为3是真，3 or 2的结果就是3
print(0 or 2)      #因为0是假，0 or 2的结果就是2
print(False or True)
print(False or "")
print("" or 2)     #因为空字符串""是假，"" or 2的结果就是2

print(3 and 2)           #因为3是真，3 and 2的结果就是2
print(0 and 2)           #因为0是假，0 and 2的结果就是0
print(False and True)
print(True and "")
print("" and 2)          #因为空字符串""是假，"" and 2的结果就是{}

x=2       # 给对象2起了一个变量名x
x+=3      # 等价于 x= x+2,即变量名x指向了原来x引用的2和3相加的结果对象。

x=3
x**=2
print(x)
x%=2
print(x)

print("h"in"hwdong")
print("h"not in"hwdong")

a = 3.14
b = 3.15
c = a
print(id(a))
print(id(b))
print(a is b)
print(a is not b)
print(a is  c)

s = "http://Hwdong.Net"
print(s)                # 用print输出s引用的字符串内容
print(len(s))           # 用len()函数得到s引用的字符串的长度，即字符个数
print(s.capitalize())   #首字母大写
print(s.upper())        #所有字母大写
print(s.lower())        #所有字母小写
print(s.rjust(20))      #右对齐
print(s.center(20))     #中心对齐
print(s.replace('//', '//www.'))    #替换
print('  hwdong '.strip()+".net")   #裁剪
print(s)

s2 = '%s %s %f' % ("The score", "of LiPing is: ", 78.5)
print(s2)

print ("{} {} {}".format("The score", "of LiPing is: ", 78.5)) 

s = "hwdong"
print(s[0], s[1], s[2], s[3], s[4], s[5])
print(s[-1],s[-5],s[-4],s[-3],s[-2],s[-1])

s = "hwdong.net"
print(s[1:6:2])
print(s[-1:-6:-2])
print(s[1:6])

score = 65.5
if score>=60:
   print("恭喜你!")
   print("通过了考试。")

score = 65.5
if score>=60:
   print("恭喜你!")
  print("通过了考试。")

score= int(input("请输入学生成绩："));
if score>=60:
    print("恭喜你!")
    print("通过了考试。")
else:
    print("你未通过考试。")
    print("继续努力，加油！")

score= int(input("请输入学生成绩："));
if score<60:
    print("不及格")
elif score<70:
    print("及格")
elif score<80:
    print("中等")
elif score<90:
    print("良好")
else:
    print("优秀");

i = 1
s = 0
while i<=100:
   s = s+i;      #等价于  s += i
   i+=1
print(s)

total_score=0
i= 0
score = float(input("请输入学生成绩："))
while True:
    total_score += score
    i += 1
    score = float(input("请输入学生成绩："))
    if  score<0:
        break                           #关键字break用于跳出循环   
    
print('平均成绩为：', total_score/i) 

for ch in "hwdong":
    print(ch,end=" ")

[1,2,3]
type([1,2,3])

my_list =[2, 3.14,True,[3,6,9],'python']
print(type(my_list))  #打印my_list的类型，即list类型
print(my_list)
print("my_list[0]:",my_list[0])
print("my_list[3]:",my_list[3])
print("my_list[-2]:",my_list[-1])
print("my_list[:]:",my_list[:])        #所有元素
my_list[2:4] = [13, 9]
print(my_list)

for e in my_list:
    print(e,end=" ")

alist = [e**2 for e in [0,1,2,3,4,5]]
print(alist)

alist = [e**2 for e in range(6)]
print(alist)

上述这种通过在[]中迭代计算产生值创建一个新list对象的式子，叫做“列表解析式”。其中还可以包括更加复杂的计算式子，如包含条件语句：

alist = [0, 1, 2, 3, 4,5]
alist = [x ** 2 for x in alist if x % 2 == 0]
print(alist)  

t = ('python',[2,5],37,3.14,"https://hwdong.net")
print(type(t))
print(t[1:4])
print(t[-1:-4:-1])

print(alist)
alist[1] = 22
print(alist)

t[1]=22

nums = (x**2 for x in range(6))
print(nums) 
for e in nums:
    print(e,end= " ")

s = {5,5,3.14,2,'python',8}
print(type(s))
print(s)

s.add("hwdong")
print(s)
s.remove("hwdong")
print(s)
alist.append("hwdong")
print(alist)
alist.insert(2,"net")
print(alist)
alist.pop()
print(alist)
alist.remove("net")
print(alist)

t.append("hwdong")

nums = {x**2 for x in range(6)}
print(nums) 

d = {1:'value', 'key':2, 'hello': [4,7]}
print(type(d))
print(d)

d['hello']

d[3]

d[3] = "python"
print(d)
print(d[3])

students={"LiPing":[21,"计科01",15370203152],"ZhangWei":[20,"计科02",17331203312]
         ,"ZhaoSi":[22,"机械03",16908092516]}
print(students)
print(students["ZhangWei"])

for name in students:
    info = students[name]
    print('{}\'s info: {} '.format(name, info))   

for key,value in students.items():
    value = students[key]
    print('{}\'s info: {} '.format(key,value)) 

points = {x:x**2 for x in range(6)}
print(points) 

#定义一个函数名是circle_area的函数
import math             #导入数学函数库math，其中有一个表示PI的常量math.pi
def circle_area():
    area = math.pi*2.5**2
    print("半径是2.5的圆面积是：%f"%area)    

circle_area()    #通过函数名circle_area调用上面的circle_area()函数

import math             
def circle_area(r):
    area = math.pi*r**2
    print("半径是%5.2f的圆面积是：%5.2f"%(r,area))    #格式符%5.2f表示输出的是float类型的数，占据5位宽，小数点后是2位

circle_area(2.5)    #通计算半径是2.5的圆面积
circle_area(3.5)    #通计算半径是3.5的圆面积

import math             
def circle(r):
    area = math.pi*r**2
    perimeter = 2*math.pi*r
    return area,perimeter    

area,p = circle(2.5)   
print("半径是2.5的圆面积和周长是：%5.2f,%5.2f"%(area,p))
area,p =circle(3.5)   
print("半径是3.5的圆面积和周长是：%5.2f,%5.2f"%(area,p))

def pow(x,n=2):
    ret = 1
    for i in range(n):
        ret *=x
    return ret

print(pow(3.5))
print(pow(3.5,3))        

def pow(a,b=2,c):
    return a+b+c

import math   
def solve_iterative(f, y, lower=0, upper=1):
    middle = (lower + upper) / 2
    while math.fabs(f(middle) - y) >= 1e-6:
        print("lower:", lower, "upper:", upper)
        if f(middle) < y:
            lower = middle
        else:
            upper = middle        
        middle = (lower + upper) / 2
    return middle

def area(r):    
    return (r ** 2) * math.pi

print("0.5和0.6之间圆面积为1的那个圆的半径是:", solve_iterative(area, 1, 0.5, 0.6))

def fact(n):
    if n==1:             #如果n等于1，就直接返回值1
        return 1
    return n * fact(n - 1)  #如果n大于1，就是n和fact(n-1)的乘积
fact(4)             # 输出： 24

s = str("http://hwdong.net")
location = s.find("hwdong")     #通过str的find()方法查询是否存在一个子串，返回子串的位置
print(location)
alist = list(range(6))
blist = alist.copy()
blist[2] = 20
print(alist)
print(blist)

class Student:
    def __init__(self, name, score):
        self.name = name
        self.score = score
        
    def print(self):
        print(self.name,",",self.score)

s1 = Student("LiPing",67)
s2 = Student("WangQiang",83)
s1.print()
s2.print()

class Student:
    count=0
    def __init__(self, name, score):
        self.name = name
        self.score = score
        Student.count +=1
        
    def print(self):
        print(self.name,",",self.score)

print(Student.count)
s1 = Student("LiPing",67)
print(s1.count)
s2 = Student("WangQiang",83)
print(Student.count)

import matplotlib.pyplot as plt

y = [i for i in range(10)]
print(y)
plt.plot(y)           #  绘制y作为纵轴坐标点构成的图形
plt.show()            #  调用plt.show()显示图形

x = [i*0.1 for i in range(10)]
y = [xi**2 for xi in x]
print(["{0:0.2f}".format(i) for i in x])
print(["{0:0.2f}".format(i) for i in y])
plt.plot(x, y)        #  绘制(x,y)坐标点构成的图形
plt.show()            #  调用plt.show()显示图形

x = [i*0.2 for i in range(10)]
y = [xi**2 for xi in x]
y2 = [3*xi-1 for xi in x]

plt.plot(x, y)        #  绘制(x,y)坐标点构成的图形
plt.plot(x, y2)  
plt.ylim(0,5)
plt.xlabel('x axis label')
plt.ylabel('y axis label')
plt.title('y=x^2 and y=3x-1')
plt.legend(['y=x^2', 'y=3x-1'])
plt.show()            #  调用plt.show()显示图形

import math
x = [i*0.2 for i in range(50)]
y = [math.sin(xi) for xi in x]
y2 = [math.cos(xi) for xi in x]
y3 = [0.2*xi for xi in x]
plt.plot(x, y,'r-')        
plt.plot(x, y2,'bo')  
plt.plot(x, y3,'g:')  
plt.legend(['sin(x)', 'cos(x)','0.2x'])
plt.show()           

import math
x = [i*0.2 for i in range(50)]
y = [math.sin(xi) for xi in x]
y2 = [math.cos(xi) for xi in x]
y3 = [0.2*xi for xi in x]
plt.scatter(x, y, c='r', s=6, alpha=0.2)        
plt.scatter(x, y2,c='g', s=18, alpha=0.9)  
plt.scatter(x, y3,c='b', s=30, alpha=0.4)  
plt.legend(['sin(x)', 'cos(x)','0.2x'])
plt.show() 

classes=['CS1901','CS1902','CS1903','CS1904','CS1905','CS1906']
scores = [76.5, 60.5, 85.0,45.5,79.3,91]
plt.bar(classes, scores, color='green')   #color参数表示颜色，'green'表示绿色
plt.xlabel('班级名')
plt.ylabel('平均分')
plt.show() 

classes=['CS1901','CS1902','CS1903','CS1904','CS1905','CS1906']
scores = [76.5, 60.5, 85.0,45.5,79.3,91]
plt.pie(scores,labels = classes, autopct='%1.1f%%')
plt.legend(loc='upper right')
plt.show() 

import random
data=[random.normalvariate(2, 3) for i in range(500)]
bins = [-8, -6, -4,-2,0,2,4,6,8,10]
plt.hist(data, bins=bins)
plt.show()

import math
x = [i*0.2 for i in range(50)]
y = [math.sin(xi) for xi in x]
y2 = [math.cos(xi) for xi in x]
y3 = [0.2*xi for xi in x]

fig = plt.gcf()
fig.set_size_inches(12, 4, forward=True)

plt.subplot(1, 2, 1)
plt.plot(x, y,'r-') 
plt.plot(x, y2,'bo')  
plt.title('sin(x) and cos(x)')
plt.legend(['sin(x)', 'cos(x)'])

plt.subplot(1, 2, 2)
plt.plot(x, y3,'g:')  
plt.title('0.2x') 


plt.show()    

import numpy as np
import skimage 
import matplotlib.pyplot as plt

img = skimage.io.imread('imgs/lenna.png')    #原图
img_tinted = img * [1, 0.95, 0.9]    #3个颜色通道值乘以不同的系数

plt.subplot(1, 2, 1)
plt.imshow(img)

plt.subplot(1, 2, 2)
plt.imshow(np.uint8(img_tinted))  #将实数值的img_tinted图像转换为unit8无符号整型
plt.show()