python3笔记

提示:

1.python对空格和缩进要求比较严格（4个空格）

2.方法、判断等结尾注意加冒号

3.不需要end等结尾

 

1.输出

print("Hello, World!")

python hello.py

 

2.判断

if 条件1:

    print("1")

elif 条件2:

    print("2")

else:

    print("3")

 

3.计算

import math

print(math.floor(32.9))

 

from math import sqrt

print(sqrt(9))

 

4.循坏输出1~5

（1）while

count = 1

while count < 6:

    print (count)

    count = count + 1

 

（2）for

for i in range(1,6):

    print(i)

 

words = ['this', 'is', 'a', 'sentence']

for word in words:

    print(word)

 

5.日期

import time

print(time.strftime("%Y-%m-%d %H:%M:%S", time.localtime()))

 

6.读取文件

f = open(r'e:/temp/1.txt')

print(f.read())

f.close()

 

readline读取1行

readlines读取所有行，返回结果为数组

write写入文件

 

7.类

class Person:

    def setName(self, name):

        self.name = name

        

    def getName(self):

        return self.name

    

    def greet(self):

        print("hello, %s." % self.name)

        

foo = Person()

foo.setName("Luke")

foo.greet()

 

8.页面简单抓取

import urllib.request

url = r'http://www.baidu.com'

res = urllib.request.urlopen(url)

html = res.read().decode('utf-8')

print(html)

 
python3之前版本

import urllib

url = r'http://www.baidu.com'

res = urllib.urlopen(url)

html = res.read().decode('utf-8')

print(html)

 

9.注释

单行注释

#print(1)

#print(2)

 

多行注释''' 或 """

'''

print(1)

print(2)

'''

 

10.字符串和数字之间转换

x = int("6")

y = str(6)

#查看类型

print(type(x))

#判断类型，返回true或false

isinstance(6, int)

 

11.字符串长度

len()

 

12.数组

#追加

data = []

data.append({"address":"beijing", "price":"100"})

data.append({"address":"shanghai", "price":"200"})

#del 根据下标删除

 

13.lambda 排序

data.sort(key=lambda z:(z["address"], z["price"]) ,reverse=True)

#reverse=True为倒叙

for d in data:

print(d)

   

14.集合反转

list = [11, 'abc', 22, 'xyz']    

print(list[::-1])

#::-2 隔一个反转    

 

15.1~100随机数

randint(1, 100)

 

16.in 操作，返回true或false

print('bc' in 'abcd')

print('nm' not in 'abcd')

 

17.string模块

import string

#首字母大写

print(string.capitalize("hello"))

#小写

string.lowercase    

"HELLO".lower()

#切割

string.split("abcdefg")

#去空格

string.lstrip(" xx")

string.rstrip("xx ")

string.rstrip(" xx ")

 

18.异常

#raise抛异常

#异常捕获

try

...

except Exception, e:

print e

finally

...

   

19.自定义高阶函数

def convert(func, seq):

return [func(eachNum) for eachNum in seq]

 

myseq = [123, 45.67, -6.263, 9999L]

#数组中每个值转为int

print(convert(int, myseq))

#数组中每个值转为long

print(convert(long, myseq))

 

20.多个参数

#默认值 rate=0.085

#多参数 *theRest

#键值对参数 **theRest

 

def taxMe(cost, rate=0.085, *theRest):

    for eachRest in theRest:

        ...

    return ...

 

def taxMe(cost, rate=0.085, **theRest):

    for eachRest in theRest,keys():

        #value = theRest[eachRest]

        ...

    return ...