Python Basic

apple_fruit=10
print(apple_fruit)

condition=1
while condition<3:
    print(condition)
    condition +=1

example_list=[1,2,3,4,5,6,7]
for i in example_list:
    print(i)
'''
Windows里面用Control [来对齐代码
MAC OS里面用Commnd [来对齐代码
'''

for i in range(1,4,2):
    print(i)

x=1
y=2
z=3
if x>y:
    print("x is greater than y")
'''
Python 和C语言一样，if elif else分支语句只会执行第一个满足条件的分支
'''

def fun(a,b):
    c=a/b
    print(c)

fun(1,2)
fun(b=2,a=1)
fun(b=1,a=2)
'''
输出，可以用参数名来明确指定参数的值，可以不按默认顺序赋值
0.5
0.5
2.0
'''

单行注释与多行注释
全局变量与局部变量

APPLE=100
def fun():
    a=10
    return a+100
print(APPLE)
#print(a) 错误 局部变量无法在这里访问


b=None
def foo():
    global b #如果没有这句，那么后面的输出也应该是None
    b=20
print('before foo:',b)
foo()
print('after foo:',b)
'''
before foo: None
after foo: 20
'''

"""
MAC OS
sudo pip3 install numpy   安装
sudo pip3 uninstall numpy     卸载
sudo pip3 install numpy-1.9.2 指定版本
sudo pip3 install -U numpy

"""

text='This is my first test.\nThis is next line.\nThis is last line.'

my_file=open('01myfile.txt','w')
my_file.write(text)
my_file.close()

append_text='\nThis is appended file.'
my_file=open('my_file.txt','a')
my_file.write(append_text)
my_file.close()

 file=open('01myfile.txt','r')
 content1=file.read()
 print(content1)
 content2=file.readlines()
 print(content2)

类，初始化，缺省参数

class Calculator:
    name='Good calculation'
    price=18
    def __init__(self,name,price,hight=18,width=29,weight=5):
        self.name=name
        self.price=price
        self.h=hight
        self.wi=width
        self.we=weight
    def add(self,x,y):
        result=x+y
        print(result)
    def minus(self,x,y):
        result=x-y
        print(result)
    def times(self,x,y):
        result=x*y
        print(result)
    def divide(self,x,y):
        result=x/y
        print(result)

输入

a=input('Please give a number:')#返回值是string,所以下面要用字符串形式
#a=int(input('Please give a number:')) 或者用int函数转换为int,那么下面直接用int即可
if a=='1':
    print('This is a good one')
elif a==str(2):
    print('See you next time')
else:
    print('Good luck')

元组与列表

#tuple list
a_tuple=(12,3,5,15,6)
another_tupl=2,4,6,8,9
a_list=[12,3,67,7,82]
for content in a_tuple:
    print(content)
for content in a_list:
    print(content)

for index in range(len(a_list)):#len 求list的元素个数 range范围函数
    print('index=',index,'number in list=',a_list[index])
"""
用双引号的多行注释,；另外python下标从0开始
index= 0 number in list= 12
index= 1 number in list= 3
index= 2 number in list= 67
index= 3 number in list= 7
index= 4 number in list= 82
"""

ap=[1,2,3,4,5,6,7,2]
ap.append(0)
print(ap)
ap.insert(1,0)#在1的位置插入0, 注意list从index 0开始
print(ap)
ap.remove(2)#移除第一个2
print(ap)
print(ap[0])#第0个元素
print(ap[-1])#最后一个元素
print(ap[1:3])#第0第1第2个元素
print(ap[3:])#3到末尾的元素
print(ap.index(5))#第一次出现5的索引
print(ap.count(4))#共有多少个4出现
ap.sort()
print(ap)
ap.sort(reverse=True)
print(ap)
"""
[1, 2, 3, 4, 5, 6, 7, 2, 0]
[1, 0, 2, 3, 4, 5, 6, 7, 2, 0]
[1, 0, 3, 4, 5, 6, 7, 2, 0]
1
0
[0, 3]
[4, 5, 6, 7, 2, 0]
4
1
[0, 0, 1, 2, 3, 4, 5, 6, 7]
[7, 6, 5, 4, 3, 2, 1, 0, 0]
"""

字典

d1={'apple':1,'pear':{1:3,3:'a'},'orange':3}#字典可以嵌套
print(d1)
d1['melon']=4
print(d1)
print(d1['pear'][3])#引用嵌套的字典
"""
{'apple': 1, 'pear': {1: 3, 3: 'a'}, 'orange': 3}
{'apple': 1, 'pear': {1: 3, 3: 'a'}, 'orange': 3, 'melon': 4}
a
"""

Module
numpy,pandas