http://blog.konghy.cn/
廖雪峰大牛
Python3教程
先来几个代码
str1 = input("请输入一个人的名字:")
str2 = input("请输入一个国家的名字:")
print("世界这么大,{}想去看看{}:".format(str1,str2))
n = input("请输入一个整数:")
sum = 0
for i in range(int(n)):
sum += i + 1
print("1到N求和的结果:",sum)
for i in range(1,10):
for j in range(1,i +1):
print("{}*{}={:2} ".format(j,i,i*j),end = '')
print('')
sum , tem = 0, 1
for i in range(1,4):
print("{}".format(i))
for i in range(1,4):
tem = i * tem
sum += tem
print("{}".format(sum))
n = 1
for i in range(5,0,-1):
n = (n + 1) << 1
print(n)
TempStr = input("")
if TempStr[0] in ['F','f']:
C = (eval(TempStr) -32 ) /1.8
print("{:.2f}C".format(C))
elif TempStr[0] in ['C','c']:
F = 1.8 * eval(TempStr) + 32
print("{:.2f}F".format(F))
else:
print("输入格式错误")
# -*- coding: utf-8 -*-
n = 123
f = 456.789
s1 = 'Hello, world'
s2 = 'Hello, \'Adam\''
s3 = r'Hello, "Bart"'
s4 = r'''Hello,
Lisa!'''
可以看看这几个输出结果,在理解一下转义字符吧
Hello, world
Hello, 'Adam'
Hello, "Bart"
Hello,
Lisa!
加入定义了一个函数,我们先不写,但是其他模块写好了,要跑一下看看效果,可是这个函数没有内容编译器会报错这个时候有一个概念
def nop():
pass
这样子让代码是可以顺利编译运行的
if age >= 18:
pass
def TestReturnValue(a, b, c, d):
return a + b, c * d
num1, num2 = TestReturnValue(1, 2, 3, 4)
print(num1, num2)
r = TestReturnValue(1, 2, 3, 4)
print(r)
运行结果
3 12
(3, 12)
Process finished with exit code 0
原来返回值是一个tuple!但是,在语法上,返回一个tuple可以省略括号,而多个变量可以同时接收一个tuple,按位置赋给对应的值,所以,Python的函数返回多值其实就是返回一个tuple,但写起来更方便。《廖雪峰老师解释》
def add_end_Right(L=None):
if L is None:
L = []
L.append('END')
return L
def add_end_False(L=[]):
L.append('END')
return L
print(add_end_Right())
print(add_end_Right())
print(add_end_Right())
print(add_end_False())
print(add_end_False())
print(add_end_False())
['END']
['END']
['END']
['END']
['END', 'END']
['END', 'END', 'END']
def Calculation(*num):
count = 0
for i in num:
count += i
return count
print(Calculation(1,2,3,4))
10
import math
dayup = math.pow((1.0 + 0.005), 365)
daydown = math.pow((1.0 - 0.005),365)
print("向上:{:.2f},向下:{:.2f}.".format(dayup,daydown))
def dayUP(df):
dayup = 0.01
for i in range(365):
if i % 7 in [6,0]:
dayup = dayup * (1 - 0.01)
else:
dayup = dayup * (1 + df)
return dayup
dayfactor = 0.01
while(dayUP(dayfactor) < 37.78):
dayfactor += 0.001
print("每天努力参数是:{:.3f}.".format(dayfactor))
原文链接
单元测试是用来对一个模块、一个函数或者一个类来进行正确性检验的测试工作。
比如对函数abs(),我们可以编写出以下几个测试用例:
输入正数,比如1、1.2、0.99,期待返回值与输入相同;
输入负数,比如-1、-1.2、-0.99,期待返回值与输入相反;
输入0,期待返回0;
输入非数值类型,比如None、[]、{},期待抛出TypeError。
把上面的测试用例放到一个测试模块里,就是一个完整的单元测试。
如果单元测试通过,说明我们测试的这个函数能够正常工作。如果单元测试不通过,要么函数有bug,要么测试条件输入不正确,总之,需要修复使单元测试能够通过。
try:
except :
except :
except:
else:
finally:
class Singleton(object):
class _A(object):
def __init__(self):
pass
def display(self):
return id(self)
_instance = None
def __init__(self):
if Singleton._instance is None:
Singleton._instance = Singleton._A()
def __getattr__(self, attr):
return getattr(self._instance, attr)
if __name__ == '__main__':
s1 = Singleton()
s2 = Singleton()
print(id(s1), s1.display())
print(id(s2), s2.display())
代码的解释
def getattr(self, attr):
return getattr(self._instance, attr)
# 例如这里有一个类 A ,,有两个属性
>>> class A:
... test1 = "this test1"
... test2 = "this test2"
...
>>>
# 然后实例化一个对象
>>> a = A()
# 就可以用 getattr 直接去获取对象 a 的属性值
>>> getattr(a, "test1")
'this test1'
>>>
>>> getattr(a, "test2")
'this test2'
>>>
http://blog.konghy.cn/2017/04/24/python-entry-program/
https://blog.csdn.net/ling_mochen/article/details/79314118#commentBox
https://blog.csdn.net/csdn_kou/article/details/83720765
学习资源是中国大学mooc的爬虫课程。《嵩天老师》
下面写几个简单的代码!熟悉这几个代码的书写以后基本可以完成需求!
import requests
r = requests.get("https://www.baidu.com")
fo = open("baidu.txt", "w+")
r.encoding = 'utf-8'
str = r.text
line = fo.write( str )
import requests
url = "https://item.jd.com/2967929.html"
try:
r = requests.get(url)
r.raise_for_status()//如果不是200就会报错
r.encoding = r.apparent_encoding//转utf-8格式
print(r.text[:1000])//只有前1000行
except:
print("False")
fo.close()
fo = open("jingdong.md","w")
url = "https://item.jd.com/2967929.html"
try:
r = requests.get(url)
r.encoding = r.apparent_encoding
demo = r.text
soup = BeautifulSoup(demo,"html.parser")
fo.write(soup.prettify())
fo.writelines(soup.prettify())
except:
print("False")
fo.close()
fo = open("baidu.md","w")
try:
r = requests.get("https://www.baidu.com")
r.encoding = r.apparent_encoding
demo = r.text
soup = BeautifulSoup(demo,"html.parser")
fo.write(soup.prettify())
fo.writelines(soup.prettify())
except:
print("False")
fo.close()
附赠
爬虫和python例子开源链接