String
# loop through
for c in "abc":
print(c)
# string replace with return the end result. It does not change original result
date = datePart.replace("th", "")
# string split to list. X will be [welcome, to, jungle]
txt = "welcome to jungle"
x = txt.split()
# substring. will print 20
datePart = "20th"
print(datePart[0:2])
#substring to the end. will print 0th
datePart = "20th"
print(datePart[1:])
# generate an array for all lower case letters (a...z)
letters = list(string.ascii_lowercase)
#convert a decimal integer to binary string. get "111"
s1 = bin(7).replace("0b", "")
#zero left fill. The length is the length of the result string
s= "123"
# get "00123"
s=s.zfill(5)
#The count() method returns the number of times a specified value appears in the string.
print ("foobar".count("o")) # print 2
# get a char's ascii value. 'a' is 97. For code below, will return 98
print(ord('b'))
#ascii value to char. here print 'a'
print(chr(97))
#find and rfind. return 0 and 4
"abcda".find("a")
"abcda".rfind("a")
# str to int. get 9 for the code below
int("09")
hash
#create hash
hash1 = {}
#initiate hash with default data. use get to set a default value. will print out 0
print (hash1.get('a', 0))
#assigin value
hash1['a'] = 10
# access hash. print out 10
count = hash1['a']
print(count)
# check if key exist in hash. should get false
if 'c' not in hash1:
print ("not have")
# loop through
for k in hash1:
print(hash1[k])
# clear or empty a hash
hash1.clear()
# get hash keys
hash1.keys()
#decouple with hash
keys = list(pointHash.keys())
array
# append. arr becomes 1,2,4
arr = [1,2]
arr.append(4)
# create two dimension array
dp = []
for i in range(n):
dp.append([10000]*n)
# find index of a element
nums = [2,3,49,1]
try:
i = nums.index(49)
except ValueError:
pass
#length
print(len(nums))
# join array into string
" ".join(nums)
# sort. This is in house sort
nums.sort()
# sort two dimention array by x[0], then x[1]
intervals.sort(key=lambda x:[x[0], x[1]])
# sort by x[0]
stockPrices.sort(key=lambda x:x[0])
# reverse in house sort
inventory.sort(reverse=True)
# pop at index
nums.pop(0)
# remove from the begin
nums.pop(0)
# remove from the end
nums.pop()
#initial array with 0
ans = [0] * 100
# initiate array with 0 (another way). The below will get [0,0,0,0,0]
arr=[]
arr = [0 for i in range(5)]
#reverse range
reversed(range(100))
#initialize two dimension array
dp = [[0 for x in range(m)] for y in range(m)]
# list comprehension
starts = [a for a, b in flowers]
ends = [b for a, b in flowers]
Set
# create a empty set
s = set()
# add an element to set
s.add(1)
# check length of set
print(len(s))
# check contains
if 2 in s:
Binary search built in functions
bisect.bisect_left(a, x, lo=0, hi=len(a)) : Returns leftmost insertion
point of x in a sorted list. Last two parameters are optional,
they are used to search in sublist.
bisect.bisect_right(a, x, lo=0, hi=len(a)) Returns rightmost insertion
point of x in a sorted list a. Last two parameters are optional,
they are used to search in sublist.
index = bisect_right(arr, val)Permutation
for p in permutations([1,2,3], 3):
print (p)
#output
(1, 2, 3)
(1, 3, 2)
(2, 1, 3)
(2, 3, 1)
(3, 1, 2)
(3, 2, 1)
Rest API
Send a post
import requests
import json
url = 'http://localhost:5000'
myobj = {'somekey': 'somevalue'}
headers = {'content-type':'application/json'}
x = requests.post(url, data =json.dumps( myobj), headers=headers)
print(x.text)
Math
#integer div.It will return 4
9//2
# find gcd of two integers
gcd = math.gcd(d, price)
# val is 8
val = max(3, 8)
#power. mod is optional. But if need mod, use it. It is
#much faster than ans=pow(x,y) ans = ans%mod
pow(x, y, mod)
ans = ans + pow(2, r-i, 1000000007)
Inner Function
def countDaysTogether(self, arriveAlice: str, leaveAlice: str, arriveBob: str, leaveBob: str) -> int:
months = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]
def getDayOfYear(dayStr:str)->int:
arrMonth = int(dayStr[0:2])
arrDay = int(dayStr[3:5])Hard questions
1799. Maximize Score After N Operations
class Solution:
myMap = {}
def maxScore(self, nums: List[int]) -> int:
def getM(k, nums):
# build cache key
cacheK = ' '.join(str(x) for x in nums)+ "k:" + str(k)
if cacheK in self.myMap:
return self.myMap[cacheK]
if len(nums)==2:
ans = k*math.gcd(nums[0], nums[1])
self.myMap[cacheK] = ans
return ans
ans =0
l = len(nums)
for i in range(l-1):
for j in range(i+1, l):
n1 = k*math.gcd(nums[i], nums[j])
left = []
for h in range(l):
if h!=i and h!=j:
left.append(nums[h])
n2 = getM(k+1, left)
if (n1+n2) > ans:
ans = n1 + n2
self.myMap[cacheK] = ans
return ans
nums.sort()
return getM(1, nums)heap
#Leetcode 2542
class Solution:
def maxScore(self, nums1: List[int], nums2: List[int], k: int) -> int:
l = len(nums1)
nums = []
for i in range(l):
nums.append([nums1[i], nums2[i]])
#sort by the second element
nums.sort(key=lambda x:x[1])
nums.reverse()
ans, curSum = 0, 0
myHeap = []
for i in range(k):
curSum += nums[i][0]
heapq.heappush(myHeap, nums[i][0])
ans = curSum * nums[k-1][1]
for i in range(k, l):
out = heapq.heappop(myHeap)
curSum = curSum-out + nums[i][0]
heapq.heappush(myHeap, nums[i][0])
ans = max(ans, curSum * nums[i][1])
return ans#Leetcode 1464
import heapq
class Solution:
def maxProduct(self, nums: List[int]) -> int:
for i in range(len(nums)):
nums[i] = nums[i]*-1
heapq.heapify(nums)
# return smallest
a = heapq.heappop(nums)
b = heapq.heappop(nums)
return (a*-1 -1) * (b*-1-1)
Run codes
#Leetcode 1992
from typing import List
class Solution:
def findFarmland(self, land: List[List[int]]) -> List[List[int]]:
def getFarm(f: List[int], a:int, b:int):
if a<f[0] or b<f[1]:
f[0]=a
f[1]=b
if a>f[2] or b>f[3]:
f[2] = a
f[3] = b
return f
rows = len(land)
cols = len(land[0])
ones = []
# find all ones
for i in range(rows):
for j in range(cols):
if land[i][j] == 1:
ones.append([i, j])
#put ans
ans = []
for one in ones:
#some one has been grouped
if land[one[0]][one[1]] != 1:
continue
# one itself is a farmland
x, y = one[0], one[1]
queue = [[x,y]]
myLand = [x, y, x, y]
while len(queue)>0:
size = len(queue)
for i in range(size):
point = queue.pop(0)
a, b = point[0], point[1]
#left
if b!=0 and land[a][b-1] == 1:
myLand = getFarm(myLand, a, b-1)
land[a][b-1] = 0
queue.append([a, b-1])
#right
if b!=cols-1 and land[a][b+1] == 1:
myLand = getFarm(myLand, a, b+1)
land[a][b+1] = 0
queue.append([a, b+1])
#up
if a!=0 and land[a-1][b]==1:
myLand = getFarm(myLand, a-1, b)
land[a-1][b] = 0
queue.append([a-1, b])
#down
if a!=rows-1 and land[a+1][b]==1:
myLand = getFarm(myLand, a+1, b)
land[a+1][b] = 0
queue.append([a+1, b])
ans.append(myLand)
return ans
obj = Solution()
land = [[1,0,0],[0,1,1],[0,1,1]]
res = obj.findFarmland(land)
print(res)django
commands
django-admin startproject project-name
python manage.py startapp app-name
python manage.py runserver
# open a shell to run some db query
python manage.py shell
Handle Form
# get post data
post_id = request.POST.get("post_id")
Use env variables
# create .env file in the project directory
api_key=mysecfretetemmsmsm
# in settings.py
from dotenv import load_dotenv
load_dotenv()
# to access env variable
import os
os.getenv("api_key")var dump
from pprint import pprint
pprint(request.POST)Versions
#find version
python -V
pip -V
python3.7 -m pip list
#show version used to store library
pip show openaiInstall Python OpenAi Module
python3.7 -m pip install --upgrade pip
python3.7 -m pip install openai
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