Python hello world

Integer/Float calculation

#######################
########## caculating #
#######################
Operator   Description   Example
+   Addition operator   100 + 45 = 145
-   Subtraction operator   500 - 65 = 435
*   Multiplication operator   25 * 4 = 100
/   Float Division Operator   10 / 2 = 5.0
//   Integer Division Operator   10 / 2 = 5
**   Exponentiation Operator   5 ** 3 = 125
%   Remainder Operator   10 % 3 = 1  #  10 / 3 = 3 ... 1

Float formate

##########print##########

pi = 3.141592653
print('%10.3f' % pi) #字段宽10，精度3
## 3.142
print("pi = %.*f" % (3,pi)) #用*从后面的元组中读取字段宽度或精度
## pi = 3.142
print('%010.3f' % pi) #用0填充空白
## 000003.142
print('%-10.3f' % pi) #左对齐
## 3.142
print('%+f' % pi) #显示正负号
## +3.141593

List

## duplicats removing
A = [1,1,1,2,3,4,3]
print(A)

Remove duplicates from list

list(set(A))

int list to str list

[str(x) for x in int_list]

or

a_list = ["1", "2", "3"]
##int list to str list
list(map(str, a_list))
##str list to int list
list(map(int, a_list))

逐个相减

c = [b[i] - a[i] for i in range(len(a))]

Compare Two list

l = [1, 2, 3, 5]
l_one = [2, 8, 6, 10]
print set(l) & set(l_one)

Time

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

Date caculating

zhengxiangwen 2017

import datetime #导入日期时间模块
today = datetime.date.today() #获得今天的日期
print today #输出今天日期
2016-01-25
yesterday = today - datetime.timedelta(days=1) #用今天日期减掉时间差，参数为1天，获得昨天的日期
print yesterday
2016-01-25
tomorrow = today + datetime.timedelta(days=1) #用今天日期加上时间差，参数为1天，获得明天的日期
print tomorrow
2016-01-25
print "昨天:%s， 今天:%s， 明天：%s" % (yesterday, today, tomorrow) #

For loop

for x in range(0,10):
  print (x,end = '')

Read/Write a file

###read file
f = open("demofile.txt", "r")
print(f.read())

with open(fname) as f:
    content = f.readlines()

### write to file
fo = open("foo.txt", "w")
fo.write( "www.runoob.com!\nVery good site!\n")

fo.close()
## wirte at the end of the file
with open('something.txt', 'a') as f:
    f.write('text to be appended')

print

A =" "
B =u"\u2581"
C =u"\u2582"
D =u"\u2583"
E =u"\u2584"
F =u"\u2585"
G =u"\u2586"
H =u"\u2587"
I =u"\u2588"

for i in A,B,C,D,E,F,G,H,I:
  print("\x1b[3;45;6m%s\x1b[0m"%(i),end='')

path

import pathlib
pathlib.Path(__file__).parent.absolute()

import pathlib
pathlib.Path().absolute()

import os
sys.path[0]

## Chage Workind Director
import os
os.chdir("../")

import

## import from the same directory
import XXX

## import from the directories in the same directory
from Directory import xxx

## import from .. directory
import sys
sys.path.append("..")
import xxx　

str to var

for i in range(4):
    name='v'+str(i)
    locals()['v'+str(i)]=i

print v1,v2,v3

Dictionary

Find the max value from a dictionary

d = {'a': 10, 'b': 5, 'c': 20}
max_value = max(d, key=d.get)
print(max_value)

c