一枚老猿的Python学习随笔（2）

本想边学习&＃xff0c;边笔记整理&＃xff0c;学了一天发现简单跟随一个教程太单一&＃xff0c;随学随记吧。

昨天在Windows10下安装了Python的开发环境&＃xff0c;今天换了电脑&＃xff0c;Windows7环境下安装&＃xff0c;遇到了Server pack 1 一个升级包的问题&＃xff1a;安装log 提示 缺少 KB2533625——ms 原有连接已经失效&＃xff0c;着实找了一番&＃xff08;已上传&＃xff09;。

PS:Windows7 下可以选择python3.8版本

再认识Python
今天&＃64;2020.10.31
浏览了Python的简单教程&＃xff0c;了解了&＃xff1a;Python的数字、字符串、布尔、运算符、列表、集合、字典、数组概念、日期、Json、正则&＃xff0c;测试了函数、Lambda&＃xff0c;Python的分支、循环&＃xff0c;类/对象、继承、迭代以及Python的错误处理机制&＃xff0c;顺便试了试简单的文件读写。
总体感觉&＃xff0c;Python语法简练&＃xff0c;各种写法支持的很好。

接下来&＃xff0c;研究下NumPy&＃xff0c;NumPy就说是访问内存连续地址空间&＃xff0c;同时硬件优化是Python内置数据处理速度的50倍&＃xff0c;所以决定试一试。

Python3.4开始&＃xff0c;集成了pip(Python包管理工具&＃xff09;。
命令行&＃xff0c;进入Python目录下&＃xff1a;…\Python\Python38\ Scripts目录

C:\Users\Admin>d:
D:\>cd D:\Users\admin\AppData\Local\Programs\Python\Python38\Scripts
D:\Users\Admin\AppData\Local\Programs\Python\Python38\Scripts>pip install numpy


安装成功&＃xff0c;测试是否OK&＃xff1a;

import numpy as np #引入 NumPy 包&＃xff0c;并重命名为 np
arr &＃61; np.array([1, 2, 3, 4, 5])
print(arr) # Result:[1,2,3,4,5]


Python 3.9版本有点高&＃xff0c;改装了3.8.6&＃xff01;&＃xff01;&＃xff01;

3、NumPy小试

Numpy包封装了丰富的数据处理方法…

4、贴段代码

测试代码

import sys
import numpy as np
import matplotlib.pyplot as plt
import requests,pymongox &＃61; requests.get(&＃39;https://w3school.com.cn/python/demopage.htm&＃39;)rtext &＃61; x.text[::-1]print(rtext)exec(&＃39;print("a"&＃43;str(100))&＃39;)sys.exit(1)
x &＃61; [1,2,3,5,6,7,8,9,10,12,13,14,15,16,18,19,21,22]
y &＃61; [100,90,80,60,60,55,60,65,70,70,75,76,78,79,90,99,99,100]mymodel &＃61; np.poly1d(np.polyfit(x, y, 3))myline &＃61; np.linspace(1, 22, 100)plt.scatter(x, y)
plt.plot(myline, mymodel(myline))
plt.show()x &＃61; np.random.uniform(0.0, 5.0, 250)plt.hist(x, 5)
plt.show()"""
arr &＃61; np.array([1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12])
newarr &＃61; arr.reshape(24,-1)
print("arrshap:"&＃43;str(arr.shape))
print(arr)
print("&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;")
print("newarrshap:"&＃43;str(newarr.shape))
print(newarr)
print(newarr.reshape(-1))arr1 &＃61; np.array([1, 2, 3])arr2 &＃61; np.array([4, 5, 6])arr &＃61; np.dstack((arr1, arr2))print(arr)
"""x &＃61; np.random.uniform(0.0, 5.0, 50001088)
print("Count:"&＃43;str(len(x)))
print(x[3333])sys.exit(0)print("Hello, World! ——Python")
if 5-3 &＃61;&＃61; 2:print("YES!")if 5 - 2&＃61;&＃61; 3:print("NO!!")#单行注释
print("也可单行后半部分注释") #打印函数
"""
块注释"""
x &＃61; y &＃61; z &＃61; 10
print(x,y,z)
x,y,z &＃61; 1,2,3
print(x,y,z)
x,y,z &＃61; 1,10,"v_x"
x &＃43;&＃61;2
z &＃43;&＃61; "_var"
print(x,y,z)
print("&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;&＃61;")
def funcA():x &＃61; 100print(x)
funcA()
print(x)x&＃61;3
print(x)
def funcB():global xx &＃61; 100print(x) #result:100
funcB()
print(x) # result:100 x,y,z &＃61; 12.5,12.80,"string"
if type(x) &＃61;&＃61; int:int("x:"&＃43;str(type(x)))
else:print(type(x))x &＃61; int(12.9)
print(x)
x &＃61; str(12.3)
print(x &＃43;"kg")x &＃61; list(("Python", "GoLang", "Java"))
print(x)x &＃61; 123.1
if type(x) &＃61;&＃61; int:y &＃61; int(x)
print("sssss")print(y)
y &＃61; 0
x &＃61; 5
if x > 10:y &＃61; int(x)y &＃43;&＃61; 3print("A" &＃43; str(y))if x > 10: y &＃61; int(x)
y &＃43;&＃61; 3
print("B" &＃43; str(y))print(bool(-2))class myclass():def __len__(self):return 10myobj &＃61; myclass()
print(bool(myobj))print(isinstance("asdf",int))x &＃61; 1
y &＃61; 11
print(1 in [1,2])""" 奇怪的for循环
s &＃61; ("a,b,c,d").split(",")
print(s)
if len(s) > 0:for x1 in s:print(x1)s.remove(x1)
"""
s &＃61; """
"""
print("s:")
s &＃61; list(s)
print(s)thisset &＃61; {"apple", "banana", "cherry"}x &＃61; thisset.pop()print(x)print(thisset)thisdict &＃61; {"brand": "Porsche", "brand1": "Porsche","model": "911","year": 1963
}
thisdict["year"] &＃61; 2019
print(thisdict)
x &＃61;8
if int(x) > 1: print("x>1")
print("a") if x>1 else print("b")i &＃61; 0
while i<&＃61;10:print(i)i &＃43;&＃61;1
else:print(i)print("else")for x in "banana":print(x)
for x in range(100,201,2):print(x)
else:print("for end")adj &＃61; ["red", "big", "tasty"]
fruits &＃61; ["apple", "banana", "cherry"]for x in adj:for y in fruits:print(x, y)


5、研究Python的另一个原因

——今日接到多个了推广Python培训的营销电话&＃xff0c;小学生定向营销&＃xff0c;真是为了挣钱没有底线&＃xff0c;孩子们能理解程序吗——或许部分天才可以&＃xff0c;个人认为学好基础文化科才是正道。

接下来系统研究 Go Lang 开发。

补充

2020-11-23
不能白学&＃xff0c;用Python写了数据生成&＃xff1a;区分大小写的序列数据&＃xff0c;运行效率还可以&＃xff0c;谁能看出这个有啥用&＃xff1f;

import sys
import numpy as np
from numpy import random
"""
生成 Codes 数据&＃xff0c;数据由
62个元素[0-9,a-z,A-Z]
n位无重复组合
"""ods &＃61; (&＃39;0&＃39;, &＃39;1&＃39;, &＃39;2&＃39;, &＃39;3&＃39;, &＃39;4&＃39;, &＃39;5&＃39;, &＃39;6&＃39;, &＃39;7&＃39;, &＃39;8&＃39;, &＃39;9&＃39;, &＃39;a&＃39;, &＃39;b&＃39;, &＃39;c&＃39;, &＃39;d&＃39;, &＃39;e&＃39;, &＃39;f&＃39;, &＃39;g&＃39;, &＃39;h&＃39;, &＃39;i&＃39;, &＃39;j&＃39;, &＃39;k&＃39;, &＃39;l&＃39;, &＃39;m&＃39;, &＃39;n&＃39;, &＃39;o&＃39;, &＃39;p&＃39;, &＃39;q&＃39;, &＃39;r&＃39;, &＃39;s&＃39;, &＃39;t&＃39;, &＃39;u&＃39;, &＃39;v&＃39;, &＃39;w&＃39;, &＃39;x&＃39;, &＃39;y&＃39;, &＃39;z&＃39;, &＃39;A&＃39;, &＃39;B&＃39;, &＃39;C&＃39;, &＃39;D&＃39;, &＃39;E&＃39;, &＃39;F&＃39;, &＃39;G&＃39;, &＃39;H&＃39;, &＃39;I&＃39;, &＃39;J&＃39;, &＃39;K&＃39;, &＃39;L&＃39;, &＃39;M&＃39;, &＃39;N&＃39;, &＃39;O&＃39;, &＃39;P&＃39;, &＃39;Q&＃39;, &＃39;R&＃39;, &＃39;S&＃39;, &＃39;T&＃39;, &＃39;U&＃39;, &＃39;V&＃39;, &＃39;W&＃39;, &＃39;X&＃39;, &＃39;Y&＃39;, &＃39;Z&＃39;)
"""
for i in range(ord("0"), ord("9")&＃43;1):ods &＃61; ods &＃43; [chr(i)]for i in range(ord("a"), ord("z")&＃43;1):ods &＃61; ods &＃43; [chr(i)]for i in range(ord("A"), ord("Z")&＃43;1):ods &＃61; ods &＃43; [chr(i)]
"""
ods_len &＃61; len(ods)print("ord_len:" &＃43; str(ods_len))
print(ods)f &＃61; open("f.dat","w")
c1&＃61;c2&＃61;c3&＃61;c4 &＃61; ""
for t1 in range(60,ods_len):c1 &＃61; ods[t1]for t2 in range(60,ods_len):c2 &＃61; ods[t2]for t3 in range(60,ods_len):c3 &＃61; ods[t3]for t4 in range(60,ods_len):c4 &＃61; ods[t4]c &＃61; c1&＃43;c2&＃43;c3&＃43;c4f.write(str(random.rand())&＃43;","&＃43;c&＃43;"\n")f.close()