Self taught neural network series - 1 Basic programming knowledge

1.1 Variable type

• integer 、 character string 、 floating-point
• list 、 Dictionaries 、 Tuples 、 Boolean type

print(type(10))
print(type(str(10)))
print(type(float(10)))

#  Definition of variables 、 Calculation 、 assignment 
#  stay python Can be operated directly in , You can also assign values to variables to perform operations on variables 
a = 10
print(a)
a = 100
print(a)
b = 3.14
print(a*b)
# python Dynamic language , The type of variable will change automatically according to the situation 

#  list 
a = [1,2,3,4,5]
len(a)
#  Indexes 
a[0]
#  assignment 
a[4]=100
print(a)
#  section 
a[1:]
a[:-1]
a[:-2]  #  The slice does not contain ： The next element 

#  Dictionaries 
me = {
    'height': 180}
#  Indexes 
me['height']
#  assignment 
me['height'] =100
me
#  Add key value 
me['weight'] = 70
me

#  Boolean type 
#  The value is True /False A variable of 
hungry = True  #  I'm hungry 
sleepy = False  #  Not sleepy 
type(hungry)
#  operation   Can only be  and or not
not hungry
hungry and sleepy
hungry  or sleepy

hungry =  True
if  hungry:
    print("I'm hungry!")
hungry = False
if  hungry:
    print("I'm hungry !")
else:
    print("I'm not hungry!")
    print("I'm sleepy!")

for i in [1,2,3]:
     print(i)

#  function 
def hello():
    print("hello world！")
hello()
#  Function passed in parameters 

def hello(object):
    print("hello "+ object +'!')

hello("cat")

#  class 
class Man:
    
    def __init__(self,name):
        self.name = name
        print("Initialized!")
    
    def hello(self):
        print("Hello " + self.name + "!")
    
    def goodbye(self):
        print("Goodbye " + self.name + "!")


def main():
    m = Man("Wang")
    m.hello()
    m.goodbye()

if __name__== "__main__":
    main()

#  Array 
#  take X Turn into 1 Is an array 
import numpy as np

x = np.array([[1,2],[3,4]])
x
x.flatten()

import numpy as np
import matplotlib.pyplot as plt

x = np.arange(0,6,0.1) #60 Number 
y1 = np.sin(x) 
y2 = np.cos(x)
plt.plot(x,y1,label="sin")
plt.plot(x,y2,linestyle="--",label='cos')
plt.xlabel("x")
plt.ylabel('y')
plt.title("sin & cos") # title 
plt.legend() #  legend 
plt.show()

#  Read image imread And display images imshow
from matplotlib.image import imread

img = imread(" cover .jpg")
plt.imshow(img)
plt.show()