Python随笔(一)、python基础

发布时间：2019-09-03 08:56:04编辑：auto阅读（1390）

在pycharm下设置自己的模板:

在File---settings---File and Code Templates---Python script 脚本里添加:

#!/usr/bin/env python 

#-*- coding:utf-8 _*-  

""" 

@author:${USER} 

@file: ${NAME}.py 

@time: ${YEAR}/${MONTH}/${DAY} 

"""  

一、第一个python程序：

#!usr/bin/env python 
#-*- coding:utf-8 _*-  
""" 
@author:Administrator 
@file: HelloWorld.py
@time: 2017/11/{DAY} 
"""
print("HelloWorld!!!")
print("你好，世界")

二、变量和赋值：
#!usr/bin/env python 
#-*- coding:utf-8 _*-  
""" 
@author:Administrator 
@file: bianliang.py
@time: 2017/11/18 
"""
#赋值
name = "chenjisong"
age = 30
print(name,age)

字符串类型的必须要加引号

a = 3
b = a
a = 5
print(a,b)

返回结果为(5,3)

解析：a = 3,内存地址指向3，b = a,则b = 3,此时a 和 b 都指向内存地址3，当 a = 5的时候，a 的内存地址指向了5，则a = 3 这个内存地址被回收了，但是b的内存地址未被回收，b仍然等于3，所以最后返回的结果是(5,3)

变量起名的原则：

      1、显示，通俗易懂

      2、驼峰写法（首字母大写）          例如：NumsOfJackGf

      3、下横线写法（不能为中横线）   例如：nums_of_jack_gf

      4、不能数字开头，但是可以在中间和结尾

      5、命名中不能有特殊字符

      6、变量的命名不能有空格

     7、关键字不能声明为变量


 内存地址的验证：

C:\Users\Administrator>python

Python 3.6.3 (v3.6.3:2c5fed8, Oct  3 2017, 18:11:49) [MSC v.1900 64 bit (AMD64)]

 on win32

Type "help", "copyright", "credits" or "license" for more information.

>>> import keyword

>>> a = 5

>>> b = a

>>> id(a),id(b)

(1363763552, 1363763552)

a 和 b的内存地址完全一样

>>> a = 10

>>> id(a),id(b)

>>> (1363763712, 1363763552)

当a的值改变之后，a的内存地址也发生了变化（是python中的内存地址，不是物理机器的内存地址）




三、用户交互


[root@python3 ~]# python
Python 3.6.3 (default, Nov 12 2017, 04:07:16)
[GCC 4.8.5 20150623 (Red Hat 4.8.5-16)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> name = input("please input your name:")
please input your name:chenjisong


>>> print(name)

chenjisong

>>> a = 5
>>> eval('a')
5

四、条件判断与缩进

IF....ELSE和缩进

伪代码：

如果   你是富二代

          我们俩就拍拖

或者   你很努力上进

          我们可以接触试试

否则

          免谈

缩进要一致：
sex = input ("plsase input your gender:")
if sex == "gril":
    print("I would like to have a baby")
elif sex == "man":
    print("going to homesexual!")
else:
    print("Pervert!!!")

游戏:猜幸运数字：


#!usr/bin/env python 
#-*- coding:utf-8 _*-  
""" 
@author:Administrator 
@file: lucky_number.py
@time: 2017/11/18 
"""
lucky_number = 18
guess_number = int(input("can you guess my lucky_number:"))
if guess_number > lucky_number:
    print("guess_number is bigger then lucky_number")
elif guess_number < lucky_number:
    print("guess_number is smaller then lucky_number:")
else:
    print("congratulations,you guess it,but no prize")




五、循环控制:

break结束循环：（猜对即跳出循环，没猜对就一直猜）


while True:   
    lucky_number = 18
    guess_number = int(input("can you guess my lucky_number:"))
    if guess_number > lucky_number:
        print("guess_number is bigger then lucky_number")
    elif guess_number < lucky_number:
        print("guess_number is smaller then lucky_number:")
    else:
        print("congratulations,you guess it,but no prize")
        break

while lucky_number != input_num:
    input_num = int(input("input the guess num:"))
    if input_num > lucky_number:
        print("the real number is smaller")
    elif input_num < lucky_number:
        print("the real number is bigger")
    else:
print("bingo")




六、循环次数限制：


#!usr/bin/env python 
#-*- coding:utf-8 _*-  
""" 
@author:Administrator 
@file: lucky_number.py
@time: 2017/11/18 
"""
lucky_number = 18
input_num=-1
guess_count = 0
#while lucky_number != input_num:
while guess_count < 3:
    input_num = int(input("input the guess num:"))
    print("guess count:",guess_count)
    if input_num > lucky_number:
        print("the real number is smaller")
    elif input_num < lucky_number:
        print("the real number is bigger")
    else:
        print("Bingo!")
        break
    guess_count += 1
else:
    print("try too many times")

两重判断：


第一重：三次猜不对直接退出(guess_count>3)，打印“try too many times”

第二重：猜对了直接打印bingo,退出

for循环猜数字游戏：


#!usr/bin/env python 
#-*- coding:utf-8 _*-  
""" 
@author:Administrator 
@file: lucky_number.py
@time: 2017/11/18 
"""
#while True:
lucky_number = 18
input_num=-1

for i in range(5):
    input_num = int(input("input the guess num:"))
    if input_num > lucky_number:
        print("the real number is smaller")
    elif input_num < lucky_number:
        print("the real number is bigger")
    else:
        print("Bingo!")
        break
else:
    print("try too many times")




七、常用数据类型

数据类型：


数字：

     int(整型)

     float(浮点型)

     long(长整型)

布尔:(True(1) 和  False(0))  真和假

字符串    str

列表        list

元祖       tuple

字典       dict

type可以查看数据类型：

>>> type(2**10)

<class 'int'>

>>> type(2.99)

<class 'float'>







八、字符串格式化

第一种写法会开辟很多内存空间，对内存资源是一种浪费，所以不建议

#!usr/bin/env python 
#-*- coding:utf-8 _*-  
""" 
@author:Administrator 
@file: string_format.py
@time: 2017/11/18 
"""
name = input("name:")
age = input("age：")
job = input("job:")

print("Information of "+ name +"\nName:" + name +"\nAge:"+ age +"\nJob:"+ job +"")

第二种写法只开辟了一块内存空间，可以有效节省内存资源，效率更优

#!usr/bin/env python 
#-*- coding:utf-8 _*-  
""" 
@author:Administrator 
@file: string_format.py
@time: 2017/11/18 
"""
name = input("name:")
age = input("age：")
job = input("job:")

print("Information of %s:\nName:%s\nAge:%s\nJob:%s" %(name,name,age,job))

%s要与后面的值一一对应，否则会报错

第三种写法：

#!usr/bin/env python 
#-*- coding:utf-8 _*-  
""" 
@author:Administrator 
@file: string_format.py
@time: 2017/11/18 
"""
name = input("name:")
age = input("age：")
job = input("job:")
msg = '''
Information of %s:
     Name:%s
     Age :%s
     Job :%s
'''   %(name,name,age,job)
print(msg)

'''   

    '''的妙用




九、列表常用操作：


strip:去掉，拿掉空格：以下例子去掉了前面的空格，但是中间的没法去掉

#!usr/bin/env python 
#-*- coding:utf-8 _*-  
""" 
@author:Administrator 
@file: string_format.py
@time: 2017/11/18 
"""
name = input("name:").strip()
age = input("age：").strip()
job = input("job:").strip()
msg = '''
Information of %s:
     Name:%s
     Age :%s
     Job :%s
'''   %(name,name,age,job)
print(msg)

输入


name:          chen    jisong


age：     22

job:                 IT

输出：

Information of chen    jisong:

     Name:chen    jisong

     Age :22

     Job :IT

也可以去掉字符：如下

#!usr/bin/env python 
#-*- coding:utf-8 _*-  
""" 
@author:Administrator 
@file: string_format.py
@time: 2017/11/18 
"""
name = input("name:").strip("chen")
age = input("age：").strip()
job = input("job:").strip()
msg = '''
Information of %s:
     Name:%s
     Age :%s
     Job :%s
'''   %(name,name,age,job)
print(msg)

输入


name:           chen    jisong


age：     22

job:                 IT

输出：

Information of jisong:

     Name:jisong

     Age :30

     Job :IT




列表索引(下标)取值:   []

[root@python3 ~]# python

Python 3.6.3 (default, Nov 12 2017, 04:07:16) 

[GCC 4.8.5 20150623 (Red Hat 4.8.5-16)] on linux

Type "help", "copyright", "credits" or "license" for more information.

>>> name_list = ["65brother","87brother","99brother"]

>>> name_list

['65brother', '87brother', '99brother']

>>> name_list[0]

'65brother'

>>> name_list[1]

'87brother'

>>> name_list[2]

'99brother'

>>> dir(name_list)

['__add__', '__class__', '__contains__', '__delattr__', '__delitem__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__getitem__', '__gt__', '__hash__', '__iadd__', '__imul__', '__init__', '__init_subclass__', '__iter__', '__le__', '__len__', '__lt__', '__mul__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__reversed__', '__rmul__', '__setattr__', '__setitem__', '__sizeof__', '__str__', '__subclasshook__', 'append', 'clear', 'copy', 'count', 'extend', 'index', 'insert', 'pop', 'remove', 'reverse', 'sort']

index        索引:

count       计数:

append    追加：

insert       插入：

pop          删除最后一个索引值

remove    删除固定的值

reverse     反转

sort           排序

extend      列表的扩展

>>> name_list

['65brother', '87brother', '99brother']

>>> name_list.append("Eric")

>>> name_list

['65brother', '87brother', '99brother', 'Eric']

>>> name_list.append("87brother")

>>> name_list

['65brother', '87brother', '99brother', 'Eric', '87brother']

>>> name_list.index("87brother")

1

>>> name_list.count("87brother")

2

>>> name_list.insert(2,"66brother")      在索引2之后加66brother

>>> name_list

['65brother', '87brother', '66brother', '99brother', 'Eric', '87brother']

>>> name_list.remove("66brother")

>>> name_list

['65brother', '87brother', '99brother', 'Eric', '87brother']

>>> name_list.pop()                               

'87brother'

>>> name_list

['65brother', '87brother', '99brother', 'Eric']

>>> name_list.reverse()

>>> name_list

['Eric', '99brother', '87brother', '65brother']

>>> name_list.sort()

>>> name_list

['65brother', '87brother', '99brother', 'Eric']

>>> name_list.append("87brother")

>>> name_list.append("87brother")

>>> name_list

['65brother', '87brother', '99brother', 'Eric', '87brother', '87brother']

要一次删除3个87brother，应当怎么做？？？

>>> for i in range(name_list.count('87brother')):

...    name_list.remove("87brother")

... 

>>> name_list

['65brother', '99brother', 'Eric']




十、列表的后续操作


[root@python3 ~]# python

Python 3.6.3 (default, Nov 12 2017, 04:07:16) 

[GCC 4.8.5 20150623 (Red Hat 4.8.5-16)] on linux

Type "help", "copyright", "credits" or "license" for more information.

>>> a = [1, 2, 4, 3, 'a', 'b']

>>> a

[1, 2, 4, 3, 'a', 'b']

>>> a.insert(1,8)     ---在索引一处插入数字

>>> a

[1, 8, 2, 4, 3, 'a', 'b']

正向切片：

>>> a[3:5]

[4, 3]

>>> a[0:7]

[1, 8, 2, 4, 3, 'a', 'b']

反向切片：

>>> a[-4:]

[4, 3, 'a', 'b']

>>> a[-4:-1]

[4, 3, 'a']

>>> a[0:7]

[1, 8, 2, 4, 3, 'a', 'b']

>>> a.sort()

Traceback (most recent call last):

  File "<stdin>", line 1, in <module>

TypeError: '<' not supported between instances of 'str' and 'int'  字符串和整型不能进行排序

>>> a[0:7]

[1, 2, 3, 4, 8, 'a', 'b']

>>> a.pop()

'b'

>>> a.pop()

'a'

>>> a.sort()

>>> a

[1, 2, 3, 4, 8]

拿掉字符串后即可进行排序

列表可以相加：

>>> a = [1,2,3,4,5,6,7,8,9]

>>> b = ["a","b","c","d","e","f","g","h","i"]

>>> a + b

[1, 2, 3, 4, 5, 6, 7, 8, 9, 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i']

>>> a.extend(b)

>>> a

[1, 2, 3, 4, 5, 6, 7, 8, 9, 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i']




十一、二进制位运算


元祖：

>>> t = (1,2,3,4)

>>> dir(t)

['__add__', '__class__', '__contains__', '__delattr__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__getitem__', '__getnewargs__', '__gt__', '__hash__', '__init__', '__init_subclass__', '__iter__', '__le__', '__len__', '__lt__', '__mul__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__rmul__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', 'count', 'index']

元祖改列表，用list方法：

>>> type(t)

<class 'tuple'>

>>> list(t)

[1, 2, 3, 4]

>>> type(t)

<class 'tuple'>

>>> a = list(t)

>>> type(a)

<class 'list'>




二进制运算：

>>> A = 10

>>> B = 50

>>> A & B              两者都真才为真

2

>>> A | B                两者有一真就为真

58

>>> A ^ B              一真一假则为真

56

>>> A >> 1            整体往右移一位

5

>>> A << 1            整体往左移一位

20

>>> B >> 1

25

>>> B << 1

100




逻辑运算符：与(and)  或(or)  非(not)

>>> sex = "man"

>>> age = 26

>>> if sex == "man" and age > 25:

...    print("time to get married")

... 

time to get married




>>> sex = "man"

>>> age = 26

>>> if sex == "man" or age < 23:

...     print("do not worried")

... 

do not worried




>>> name_list=["oldboy","alex","eric"]

>>> if "jack" not in name_list:

...      print("sorry")

... 

sorry




身份运算符(is    is not)

>>> name_list=["oldboy","alex","eric"]

>>> type(name_list) is tuple

False

>>> type(name_list) is list

True

>>> type(name_list) is not list

False

>>> type(name_list) is not tuple

True




十二、简单的嵌套循环

continue  跳出本次循环，继续下一次循环：





#!usr/bin/env python 
#-*- coding:utf-8 _*-  
""" 
@author:Administrator 
@file: cotinue.py
@time: 2017/11/19 
"""  
for i in range(10):
    if i < 5:
        continue
    print(i)

执行结果如下：

E:\Python36\python.exe C:/Users/Administrator/PycharmProjects/S12/2017-11-18/cotinue.py

5

6

7

8

9




#!usr/bin/env python 
#-*- coding:utf-8 _*-  
""" 
@author:Administrator 
@file: cotinue.py
@time: 2017/11/19 
"""
for j in range(5):
    for i in range(10):
        if i < 5:
            continue
        if j> 3:
            break
        print(i)

执行结果：

5

6

7

8

9

5

6

7

8

9

5

6

7

8

9

5

6

7

8

9




十三、文件的基本操作


读取文件的内容：

一次性加载所有内容到内存

obj.read()

一次性加载所有内容到内存，并根据行分割成字符串

obj.readlines()

每次仅读取一行数据：

for line in obj:

     print line

写入文件内容：

obj.write(“内容”)

关闭文件句柄：

obj.close()




打开文件：

file_obj = file("文件路径","模式")

file_obj = open("文件路径","模式")

打开文件的模式有：

r          以只读方式打开文件。

w         打开一个文件只用于写入。

a          打开一个文件用于追加。

w+       打开一个文件用于读写。

写文件的操作：

#!usr/bin/env python 
#-*- coding:utf-8 _*-  
""" 
@author:Administrator 
@file: file_opr.py
@time: 2017/11/19 
"""
f = open("test.log","w")
f.write("this is the first line\n")
f.write("this is the second line\n")
f.write("this is the third line\n")
f.write("this is the fourth line\n")
f.close()

test.log下面的文字：


this is the first line
this is the second line
this is the third line
this is the fourth line




读文件的操作，循环逐行读取：


#!usr/bin/env python 
#-*- coding:utf-8 _*-  
""" 
@author:Administrator 
@file: file_opr.py
@time: 2017/11/19 
"""
f = open("test.log","r")
#f.write("this is the first line\n")
#f.write("this is the second line\n")
#f.write("this is the third line\n")
#f.write("this is the fourth line\n")
for line in f:
    print (line)，
f.close()

执行结果：

this is the first line

this is the second line

this is the third line

this is the fourth line

判断：


#!usr/bin/env python 
#-*- coding:utf-8 _*-  
""" 
@author:Administrator 
@file: file_opr.py
@time: 2017/11/19 
"""
f = open("test.log","r")
#f.write("this is the first line\n")
#f.write("this is the second line\n")
#f.write("this is the third line\n")
#f.write("this is the fourth line\n")
for line in f:
   if "third" in line:
       print ("this is 3 line")
   else:
       print(line)
f.close()

追加文件操作:

#!usr/bin/env python 
#-*- coding:utf-8 _*-  
""" 
@author:Administrator 
@file: file_opr.py
@time: 2017/11/19 
"""
f = open("test.log","a")
#f.write("this is the first line\n")
#f.write("this is the second line\n")
#f.write("this is the third line\n")
#f.write("this is the fourth line\n")
#for line in f:
#   if "third" in line:
#       print ("this is 3 line")
#   else:
#       print(line)
f.write("8\n")
f.write("9\n")
f.write("5\n")
f.write("6\n")
f.write("7\n")
f.close()

test.log输出结果：

this is the first line
this is the second line
this is the third line
this is the fourth line
8
9
5
6
7

关键字：