我教宝宝学AI （二）基础知识

最新推荐文章于 2024-09-05 21:59:53 发布

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一、git基本使用

git是LINUX创始人为适应分布式源码管理的需求而开发的源码管理工具。在这里先介绍git的本地管理，然后再介绍如何把工作成果push到服务器端。

git本地文件有四种状态：untracked、unmodified、modified和staged。

untracked：没有加入到git本地库管理的文件，可以通过git add命令加入；

unmodified：没有被修改的文件；

modified：修改了内容的文件；

staged：等待commit

本地库主要使用命令：

1）初始化本地库

进入相应的源码目录，执行git init。

2) 往本地库里加文件

git add <filename>

增加后的文件状态为staged，可以commit后转到unmodified状态。

3) 提交文件

git commit -m "comments for modifying"

4) 创建branch

git branch dev

创建一个新的分支，并指向此branch

5) 切换branch

git checkout master

6) 查看log

git log --oneline --graph

7) 查看status

git status -s

与github同步：

1）上传源码到github

git push -u https://github.com/xxx/xxx.git

在MacOS中第一次输入用户名和密码后会记住。

2）下载源码

git clone https://github.com/xxx/xxx.git

git是分布式的源码管理工具，如果需要集中管理和严格授权，还是建议使用svn。

二、python

python是一种解释性执行高级编程语言。使用者众多，涉及各行业，在各行业累积运行良好的程序包，达到了众人拾柴火焰高的良性循环状态。python已经成为应用研究和工作即时使用的重要工具。python推荐安装anaconda版本，集成了jupter notebook等其他工具。

1) 数据类型

数字类型：

x = 3
print(type(x)) # Prints "<class 'int'>"
print(x)       # Prints "3"
print(x + 1)   # Addition; prints "4"
print(x - 1)   # Subtraction; prints "2"
print(x * 2)   # Multiplication; prints "6"
print(x ** 2)  # Exponentiation; prints "9"
x += 1print(x)  # Prints "4"
x *= 2print(x)  # Prints "8"
y = 2.5print(type(y)) # Prints "<class 'float'>"
print(y, y + 1, y * 2, y ** 2) # Prints "2.5 3.5 5.0 6.25"

布尔类型：

t = True
f = False
print(type(t)) # Prints "<class 'bool'>"
print(t and f) # Logical AND; prints "False"
print(t or f)  # Logical OR; prints "True"
print(not t)   # Logical NOT; prints "False"
print(t != f)  # Logical XOR; prints "True"

字符类型：

hello = 'hello'    # String literals can use single quotes
world = "world"    # or double quotes; it does not matter.
print(hello)       # Prints "hello"
print(len(hello))  # String length; prints "5"
hw = hello + ' ' + world  # String concatenation
print(hw)  # prints "hello world"
hw12 = '%s %s %d' % (hello, world, 12)  
print(hw12)  # prints "hello world 12"

列表类型：

xs = [3, 1, 2]    # Create a list
print(xs, xs[2])  # Prints "[3, 1, 2] 2"
print(xs[-1])     # prints "2"
xs[2] = 'foo'     # Lists can contain elements of different types
print(xs)         # Prints "[3, 1, 'foo']"
xs.append('bar')  
print(xs)         # Prints "[3, 1, 'foo', 'bar']"
x = xs.pop()      # Remove and return the last 
print(x, xs)      # Prints "bar [3, 1, 'foo']"

字典类型：

d = {'cat': 'cute', 'dog': 'furry'}  
print(d['cat'])    # prints "cute"
print('cat' in d)  # prints "True"
d['fish'] = 'wet'     # Set an entry in a dictionary
print(d['fish'])      # Prints "wet"# print(d['monkey'])  
print(d.get('monkey', 'N/A'))  # prints "N/A"
print(d.get('fish', 'N/A'))    # prints "wet"
del d['fish']         
print(d.get('fish', 'N/A')) # prints "N/A"

集合类型：

animals = {'cat', 'dog'}
print('cat' in animals)   
print('fish' in animals)  # prints "False"
animals.add('fish')       # Add an element to a set
print('fish' in animals)  # Prints "True"
print(len(animals))       # Number of elements in a set; prints "3"
animals.add('cat')        
print(len(animals))       # Prints "3"
animals.remove('cat')     # Remove an element from a set
print(len(animals))       # Prints "2"

2) 语句
循环语句：

animals = ['cat', 'dog', 'monkey']
for animal in animals:
    print(animal)# Prints "cat", "dog", "monkey"

if判断语句：

if x > 0:
    str = 'positive'
elif x < 0:
    str = 'negative'
else:
    str = 'zero'

函数：

def hello(name, loud=False):
    if loud:
        print('HELLO, %s!' % name.upper())
    else:
        print('Hello, %s' % name)

hello('Bob') 
hello('Fred', loud=True)  # Prints "HELLO, FRED!"

类：

class Greeter(object):
    # Constructor
    def __init__(self, name):
        self.name = name  # Create an instance variable

    # Instance method
    def greet(self, loud=False):
        if loud:
            print('HELLO, %s!' % self.name.upper())
        else:
            print('Hello, %s' % self.name)

g = Greeter('Fred')  
g.greet()
g.greet(loud=True)

三、Python第三方库

1）Numpy
矩阵：

import numpy as np
a = np.array([1, 2, 3])   # Create a rank 1 array
print(type(a))     # Prints "<class 'numpy.ndarray'>"
print(a[0], a[1], a[2])   # Prints "1 2 3"
a[0] = 5                  
print(a)      # Prints "[5, 2, 3]"
b = np.array([[1,2,3],[4,5,6]])    # 矩阵2*3
print(b[0, 0], b[0, 1], b[1, 0])   # Prints "1 2 4"

import numpy as np
a = np.zeros((2,2))   # Create an array of all zeros
print(a)   # Prints "[[ 0.  0.]
           #          [ 0.  0.]]"
b = np.ones((1,2))    # Create an array of all ones
print(b)        # Prints "[[ 1.  1.]]"
c = np.full((2,2), 7)  # Create a constant array
print(c)      # Prints "[[ 7.  7.]
              #          [ 7.  7.]]"
d = np.eye(2)      # Create a 2x2 identity matrix
print(d)           # Prints "[[ 1.  0.]
                   #          [ 0.  1.]]"
e = np.random.random((2,2))  
print(e)    # Might print "[[ 0.91940167  0.08143941]
            #               [ 0.68744134  0.87236687]]"

import numpy as np
# Create the following rank 2 array with shape (3, 4)
# [[ 1  2  3  4]
#  [ 5  6  7  8]
#  [ 9 10 11 12]]
a = np.array([[1,2,3,4], [5,6,7,8], [9,10,11,12]])
b = a[:2, 1:3]
print(a[0, 1])   # Prints "2"
b[0, 0] = 77
print(a[0, 1])   # Prints "77"

矩阵运算：

import numpy as np
x = np.array([[1,2],[3,4]], dtype=np.float64)
y = np.array([[5,6],[7,8]], dtype=np.float64)

# [[ 6.0  8.0]
#  [10.0 12.0]]
print(x + y)
print(np.add(x, y))
print(x - y)
print(np.subtract(x, y))
print(x * y)
print(np.multiply(x, y))
print(x / y)
print(np.divide(x, y))
print(np.sqrt(x))

2) SciPy 图像操作

from scipy.misc import imread, imsave, imresize
img = imread('assets/cat.jpg')
print(img.dtype, img.shape)  
# Prints "uint8 (400, 248, 3)"

img_tinted = img * [1, 0.95, 0.9] 
img_tinted = imresize(img_tinted, (300, 300))

imsave('assets/cat_tinted.jpg', img_tinted)