本文详细介绍了Python的基本用法，包括交互模式、变量定义、输入输出、条件语句、循环结构等核心概念。同时，深入探讨了Python2与Python3的差异，如输入功能的不同，以及数据类型和类型转换的方法。
文章目录
python的交互模式，ipython
python和ipython的区别是ipython不仅支持python语法，也支持shell指令
ubuntu@ubuntu-Lenovo:~$ ipython3
Python 3.4.3 (default, Nov 12 2018, 22:25:49)
Type "copyright", "credits" or "license" for more information.
IPython 1.2.1 -- An enhanced Interactive Python.
? -> Introduction and overview of IPython's features.
%quickref -> Quick reference.
help -> Python's own help system.
object? -> Details about 'object', use 'object??' for extra details.
In [1]: ls
11.txt Oracle_VM_VirtualBox_Extension_Pack-5.2.22.vbox-extpack
1.wav Oracle_VM_VirtualBox_Extension_Pack-6.0.0.vbox-extpack
2.1.0.201909191925_RS/ Pictures/
2.1.0.201909191925_RS.rar Public/
audio_log.sh* pychame_project/
AX2129_V005_20190830_DCC_sign/ ripgrep_11.0.2_amd64.deb
AX2129_V005_20190830_DCC_sign.zip setup64*
AX2129_V006_20190917_DCC_sign/ share/
AX2129_V006_20190917_DCC_sign.zip smartgit-19_1_5-2336c4e758ed42587f927f02537401d414ab0759.deb
bin/ sogoupinyin_2.2.0.0108_amd64.deb
brepo/ Source Insight/
client.ovpn sourceinsight_proj/
Desktop/ SP_Flash_Tool_exe_Linux_v5.1924.00.101/
Documents/ SP_Flash_Tool_exe_Linux_v5.1928.01.100/
Downloads/ SP_Flash_Tool_exe_Linux_v5.1928.01.100.zip
#ubuntu下安装ipython version2
sudo apt-get install ipython
#ubuntu下安装ipython version3
sudo apt-get install ipython3
python2的中文解决
python version 2不支持注释中有中文，怎么解决呢？
在代码的最前面添加
#coding=utf-8
或者
#-*- coding:utf-8 -*- #python推荐使用
python 注释
注释有三种写法：
1.井号#，#右边为注释的内容
2.’’'注释内容’‘’ #三个单引号之间
3.""“注释内容”"" #三个双引号之间
定义变量，使用变量
在一个程序中一个变量第一次出现，那边就是定义变量，之后在操作这个变量就是使用变量
比如：
#coding=utf-8
value = 10 #定义变量
value = value + 10 #变量赋值使用
print(value) #打印变量
输入输出
high = input("please input your high:")#输入
print("your high is %s" %high) # %high之前不能有逗号，可以有空格
print("your high is "， high) # 不用指定输出的类型%s,需要加逗号
>>> a = "lao"
>>> b = "wang"
>>> print("name = %s" %(a+b))
name = laowang
>>> print("name = ",a+b)
name = laowang
python2和python3的输入功能不同
#ipython默认使用python2
ubuntu@ubuntu-Lenovo:/work/python$ ipython
Python 2.7.6 (default, Nov 13 2018, 12:45:42)
Type "copyright", "credits" or "license" for more information.
IPython 1.2.1 -- An enhanced Interactive Python.
? -> Introduction and overview of IPython's features.
%quickref -> Quick reference.
help -> Python's own help system.
object? -> Details about 'object', use 'object??' for extra details.
In [1]: a = input("please input value:")
please input value:laowang
---------------------------------------------------------------------------
NameError Traceback (most recent call last)
<ipython-input-1-8e3b95b3288a> in <module>()
----> 1 a = input("please input value:")
<string> in <module>()
NameError: name 'laowang' is not defined
In [2]: a = input("please input value:")
please input value:1+2
In [3]: a
Out[3]: 3
注意：python2中的input()函数，输入的内容默认当成代码去执行了，而不是字符串
ubuntu@ubuntu-Lenovo:/work/python$ ipython3
Python 3.4.3 (default, Nov 12 2018, 22:25:49)
Type "copyright", "credits" or "license" for more information.
IPython 1.2.1 -- An enhanced Interactive Python.
? -> Introduction and overview of IPython's features.
%quickref -> Quick reference.
help -> Python's own help system.
object? -> Details about 'object', use 'object??' for extra details.
In [1]: a = input("please input value:")
please input value:laowang
In [2]: a
Out[2]: 'laowang'
In [3]: a = input("please input value:")
please input value:1+2
In [4]: a
Out[4]: '1+2'
In [5]:
python3中使用的input()函数的输入，是当成字符串的。
那么如何解决python2中的这个问题？
在python2中使用raw_input()，python3中没有raw_input()
ubuntu@ubuntu-Lenovo:/work/python$ ipython
Python 2.7.6 (default, Nov 13 2018, 12:45:42)
Type "copyright", "credits" or "license" for more information.
IPython 1.2.1 -- An enhanced Interactive Python.
? -> Introduction and overview of IPython's features.
%quickref -> Quick reference.
help -> Python's own help system.
object? -> Details about 'object', use 'object??' for extra details.
In [1]: a = raw_input("please input value:")
please input value:laowang
In [2]: a
Out[2]: 'laowang'
In [3]: a = raw_input("please input value:")
please input value:1+2
In [4]: a
Out[4]: '1+2'
类型及类型转换
变量定义的时候，不用管你定义的变量类型是什么，你写好之后，python编译器自动会识别你定义的变量类型，比如 a = 100,编译器自动会识别变量a的类型是int无符号整型。
判断变量的数据类型函数 type()
ubuntu@ubuntu-Lenovo:/work/python$ ipython3
Python 3.4.3 (default, Nov 12 2018, 22:25:49)
Type "copyright", "credits" or "license" for more information.
IPython 1.2.1 -- An enhanced Interactive Python.
? -> Introduction and overview of IPython's features.
%quickref -> Quick reference.
help -> Python's own help system.
object? -> Details about 'object', use 'object??' for extra details.
In [1]: a = 100
In [2]: b = 3.1415
In [3]: c = "laowang"
In [4]: type(a)
Out[4]: builtins.int
In [5]: type(b)
Out[5]: builtins.float
In [6]: type(c)
Out[6]: builtins.str
Python3 中有六个标准的数据类型：
Number（数字）–>(int、float、bool、complex（复数）)
String（字符串）
List（列表）
Tuple（元组）
Set（集合）
Dictionary（字典）
Python3 的六个标准数据类型中：
不可变数据（3 个）：Number（数字）、String（字符串）、Tuple（元组）；
可变数据（3 个）：List（列表）、Dictionary（字典）、Set（集合）。
input获取的所有数据，都当作字符串类型
#if.py
age = input("please input your age:")
if age > 18:
print("You can go to the internat bar")
ubuntu@ubuntu-Lenovo:/work/python$ python3 if.py
please input your age:17
Traceback (most recent call last):
File "if.py", line 3, in <module>
if age > 18:
TypeError: unorderable types: str() > int()
#if.py
age = input("please input your age:")
age_num = int(age)
if age_num > 18:
print("You can go to the internat bar")
ubuntu@ubuntu-Lenovo:/work/python$ python3 if.py
please input your age:19
You can go to the internat bar
int(x,base)
int() 函数用于将一个字符串或数字转换为整型
x – 字符串或数字。
base – 进制数，默认十进制。
>>>int() # 不传入参数时，得到结果0
0
>>> int(3)
3
>>> int(3.6)
3
>>> int('12',16) # 如果是带参数base的话，12要以字符串的形式进行输入，12 为 16进制
18
>>> int('0xa',16)
10
>>> int('10',8)
8
if
if 条件:
(Tab键)*******
else:
(Tab键)******
if-else
#if-else.py
age = input("please input your age:")
if age > 18:
print("You can go to the internat bar")
else:
print("You can go home now")
if-elif-else
if 条件:
(Tab键)*******
elif 条件:
(Tab键)******
elif 条件:
(Tab键)******
else：
(Tab键)******
1
2 age = int(input("please input your age:"))
3
4 if age >= 18:
5 print("You can go to the internet bar")
6 elif age >=16 and age < 18:
7 print("your age is 16---18")
8 else:
9 print("You can go home")
if嵌套
1
2 ticket = int(input("Do you have a ticket? 1 or 0\n"))
3
4 if ticket == 1:
5 print("You can pull in")
6 Knife = int(input("Do you have a knife? 1 or 0\n"))
7 if Knife == 1:
8 KnifeLength = int(input("How long is it?\n")) #cm
9 if KnifeLength <= 10:
10 print("You can get on the train")
11 else:
12 print("Waiting for check")
13 else:
14 print("You can get on the train,and have not knift")
15 else:
16 print("You should buy the ticket")
while
while 条件：
（tab键）*****
例子：
1 num = 0;
2
3 while num <= 10:
4 print(num)
5 num += 1
三角形
i = 1
while i <= 9:
j = 1
while j <= i:
print("*",end = "") # print默认带有换行符，end=""标识不换行
j += 1
print("")
i += 1
#结果
ubuntu@ubuntu-Lenovo:/work/python$ python3 triangle.py
*
**
***
****
*****
******
*******
********
*********
如果打印代码换成 print("*",end = " ")，结果为：
ubuntu@ubuntu-Lenovo:/work/python$ python3 triangle.py
*
* *
* * *
* * * *
* * * * *
* * * * * *
* * * * * * *
* * * * * * * *
* * * * * * * * *
99乘法表
i = 1
while i <= 9:
j = 1
while j <= i:
print("%d*%d=%d"%(j, i, i*j),end="\t")
#注意 print("%d*%d=%d"（这里不能加，逗号）%(j, i, i*j),end="\t")，\t是tab键
j += 1
print("")
i += 1
结果：
ubuntu@ubuntu-Lenovo:/work/python$ python3 99_multiplication_table.py
1*1=1
1*2=2 2*2=4
1*3=3 2*3=6 3*3=9
1*4=4 2*4=8 3*4=12 4*4=16
1*5=5 2*5=10 3*5=15 4*5=20 5*5=25
1*6=6 2*6=12 3*6=18 4*6=24 5*6=30 6*6=36
1*7=7 2*7=14 3*7=21 4*7=28 5*7=35 6*7=42 7*7=49
1*8=8 2*8=16 3*8=24 4*8=32 5*8=40 6*8=48 7*8=56 8*8=64
1*9=9 2*9=18 3*9=27 4*9=36 5*9=45 6*9=54 7*9=63 8*9=72 9*9=81
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