Introduction to the origin and use of Python

As can be seen from the above figure, the usage rate of python language is on the rise, and the usage rate of the top three languages ​​is on the rise. Downtrend.

PythonAdvantages and Disadvantages

Advantages:

1. Python’s positioning is “elegant”, "Clear" and "simple", so Python programs always seem simple and easy to understand. Beginners learning Python are not only easy to get started, but also can write very, very complex programs if they go deeper in the future.

2. The development efficiency is very high. Python has a very powerful third-party library. Basically, if you want to realize any function through the computer, the official Python library has corresponding modules to support it. Download it directly. After the call, development is carried out on the basis of the basic library, which greatly reduces the development cycle and avoids reinventing the wheel.

3. High-level language————When you write a program in Python, you don’t need to think about low-level details such as how to manage the memory used by your program

4. Portability - Due to its open source nature, Python has been ported to many platforms (with modifications to enable it to work on different platforms). If you carefully avoid using system-dependent features, then all of your Python programs can run without modification on almost any system platform on the market

5. Scalability———— — If you need a critical piece of your code to run faster or want certain algorithms to be kept private, you can write parts of your program in C or C++ and use them in your Python program.

6. Embeddability - You can embed Python into your C/C++ program to provide scripting functionality to your program users.

Disadvantages:

1. Slow speed. Python’s running speed is indeed much slower than C language, and it is also slower than JAVA. Therefore, this is also the main reason why many so-called experts disdain to use Python, but in fact, the slow running speed referred to here cannot be directly perceived by users in most cases, and must be reflected with the help of testing tools. For example, if you use C It took 0.01s to run a program, and 0.1s in Python. In this way, C language is directly 10 times faster than Python, which is very exaggerated, but you cannot directly perceive it with the naked eye, because the time that a normal person can perceive is the smallest The unit is about 0.15-0.4s, haha. In fact, in most cases, Python can fully meet your program speed requirements, unless you want to write a search engine that has extremely high speed requirements. In this case, of course, it is recommended that you use C to implement it.

2. The code cannot be encrypted because PYTHON is an interpreted language and its source code is stored in the form of text. However, I don’t think this is a disadvantage. If your project requires source code The code must be encrypted, so you shouldn't use Python to implement it in the first place.

3. Threads cannot take advantage of the problem of multiple CPUs. This is one of the most criticized shortcomings of Python. GIL is the Global Interpreter Lock (Global Interpreter Lock), which is used by computer programming language interpreters to synchronize threads. Tools enable only one thread to be executed at any time. Python threads are native threads of the operating system. It is pthread on Linux and Win thread on Windows. The execution of the thread is completely scheduled by the operating system. A python interpreter process has a main thread and multiple user program execution threads. Even on multi-core CPU platforms, parallel execution of multi-threads is prohibited due to the existence of GIL. Regarding the compromise solution to this problem, we will discuss it in detail in the thread and process chapters later.

1、下载安装包

2、安装
安装在C:\Python36
3、配置环境变量
【右键计算机】--》【属性】--》【高级系统设置】--》【高级】--》【环境变量】--》【在第二个内容框中找到 变量名为Path 的一行，双击】 --> 【Python安装目录追加到变值值中，用;分割】

1.解压
tar xf Python-3.6.2.tgz
2.编译安装
cd Python-3.6.2
./configure --prefix=/usr/local/Python3.6
make
make install
3.配置环境变量
vim /etc/profile
PATH=/usr/local/Python3.6/bin:$PATH
source /etc/profile
4.测试
python3.6

#!/usr/binl/env python
#encoding: utf-8
#author: YangLei

print("hello,world")

#!/usr/binl/env python
#encoding: utf-8
#author: YangLei

name = "yanglei"
print(name)

#!/usr/binl/env python
#encoding: utf-8
#author: YangLei

input_name = input("Please enter your name: ")
print("hi,%s" % input_name)

"hello world"

#!/usr/binl/env python
#encoding: utf-8
#author: YangLei

name = "yanglei"
print("hi,%s" % name)

#输出hi,yanglei

#!/usr/binl/env python
#encoding: utf-8
#author: YangLei

name = ["yanglei","jack","marry","andy"]

#!/usr/binl/env python
#encoding: utf-8
#author: YangLei

user_info = {"name":"yanglei","age":23,"job":"IT"}

#!/usr/binl/env python
#encoding: utf-8
#author: YangLei

input_user = input("Please enter your user name: ")
input_password = input("Please enter your password: ")
if input_user == "yanglei" and input_password == "123456":
    print("\033[32;1m%s login successfully\33[0m" % input_user)
else:
    print("\033[31;1mThe user name or password error,please try again\033[0m")

#!/usr/binl/env python
#encoding: utf-8
#author: YangLei

guess_age = 50
input_age = int(input("Please enter your guess age: "))
if input_age > guess_age:
    print("\033[31;1mCan you guess what big\33[0m")
elif input_age < guess_age:
    print("\033[31;1mCan you guess what small\33[0m")
else:
    print("\033[32;1mYou guessed it\33[0m")

#!/usr/binl/env python
#encoding: utf-8
#author: YangLei

count = 1
while count <= 10:
    if count == 5:
        count += 1
        continue
    print(count)
    count += 1

#!/usr/binl/env python
#encoding: utf-8
#author: YangLei

count = 1
while count <= 10:
    if count == 5:
        count += 1
        break
    print(count)
    count += 1

#!/usr/bin/env pyhon
#encoding: utf-8
#auth: yanglei

count = 0
while count < 3:
    input_user = input("Please enter your user name: ")
    input_password = input("Please enter your password: ")
    if input_user == "yanglei" and input_password == "123456":
        print("\033[32;1m%s login successfully\33[0m" % input_user)
        break
    elif count == 2:
        print("\033[31;1mThe user name or password mistake,three chances to use up,the program exits\33[0m")
        break
    else:
        count += 1
        print("\033[31;1mThe user name or password error,please try again\033[0m")

#!/usr/bin/env pyhon
#encoding: utf-8
#auth: yanglei

guess_age = 50
count = 0
while count <= 3:
    if count == 3:
        input_choose = input("Do you want to continue to play?(Y or y|N or n)")
        if input_choose == "Y" or input_choose == "y":
            count = 0
            continue
        elif input_choose == "N" or input_choose == "n":
            break
        else:
            print("\033[31;1mAre you input errors!\33[0m")
            continue
    input_age = int(input("Please enter your guess age: "))
    if input_age > guess_age:
        print("\033[31;1mCan you guess what big\33[0m")
        count += 1
    elif input_age < guess_age:
        print("\033[31;1mCan you guess what small\33[0m")
        count += 1
    else:
        print("\033[32;1mYou guessed it\33[0m")
        break