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how to iterate array of dictionary without loop using django? - python

This my scenario. I have 30 records in the array of dictionary in django. So, I tried to iterate it's working fine. but it takes around one minute. How to reduce iteration time. I tried map function but it's not working. How to fix this and I will share my example code.
Example Code
def find_places():
data = [{'a':1},{'a':2},{'a':3},{'a':4},{'a':5},{'a':6},{'a':7},{'a':8}]
places =[]
for p in range(1,len(data)):
a = p.a
try:
s1 = sample.object.filter(a=a)
except:
s1 = sample(a=a)
s1.save()
plac={id:s1.id,
a:s1.a}
places.append(plac)
return places
find_places()
I need an efficient way to iterate the array of objects in python without a loop.

You can filter outside the loop and run get_or_create instead of reverting to an object creation if the filter doesn't match.
data_a = [d.a for d in data]
samples = sample.objects.filter(a__in=data_a)
places = []
for a in data_a:
s1, created = samples.get_or_create(
a=a
)
place = {id: s1.id, a:s1.a}
places.append(place)

You can try this:
You can create a list hen save it at once, try this:
def find_places():
data = [{'a':1},{'a':2},{'a':3},{'a':4},{'a':5},{'a':6},{'a':7},{'a':8}]
places =[]
lst = []
for p in data:
a = p['a']
lst.append(a) # store it at once
Then try to store it into database. You can search: How to store a list into Model in Django.
I only made changes to loop of the code, if database side also fails you can let me know.

Related

I've followed a tutorial to write a Flask REST API and have a special request about a Python code.
The offered code is following:
# data list is where my objects are stored
def put_one(name):
list_by_id = [list for list in data_list if list['name'] == name]
list_by_id[0]['name'] = [new_name]
print({'list_by_id' : list_by_id[0]})
It works, which is nice, and even though I understand what line 2 is doing, I would like to rewrite it in a way that it's clear how the function iterates over the different lists. I already have an approach but it returns Key Error: 0
def put(name):
list_by_id = []
list = []
for list in data_list:
if(list['name'] == name):
list_by_id = list
list_by_id[0]['name'] = request.json['name']
return jsonify({'list_by_id' : list_by_id[0]})
My goal with this is also to be able to put other elements, that don't necessarily have the type 'name'. If I get to rewrite the function in an other way I'll be more likely to adapt it to my needs.
I've looked for tools to convert one way of coding into the other and answers in forums before coming here and couldn't find it.

It may not be beatiful code, but it gets the job done:
def put(value):
for i in range(len(data_list)):
key_list = list(data_list[i].keys())
if data_list[i][key_list[0]] == value:
print(f"old value: {key_list[0], data_list[i][key_list[0]]}")
data_list[i][key_list[0]] = request.json[test_key]
print(f"new value: {key_list[0], data_list[i][key_list[0]]}")
break
Now it doesn't matter what the key value is, with this iteration the method will only change the value when it finds in the data_list. Before the code breaked at every iteration cause the keys were different and they played a role.

I'm a student in a Computing class and we have to write a program which contains file handling and a sort. I've got the file handling done and I wrote out my sort (it's a simple sort) but it doesn't sort the list. My code is this:
namelist = []
scorelist = []
hs = open("hst.txt", "r")
namelist = hs.read().splitlines()
hss = open("hstscore.txt","r")
for line in hss:
scorelist.append(int(line))
scorelength = len(scorelist)
for i in range(scorelength):
for j in range(scorelength + 1):
if scorelist[i] > scorelist[j]:
temp = scorelist[i]
scorelist[i] = scorelist[j]
scorelist[j] = temp
return scorelist
I've not been doing Python for very long so I know the code may not be efficient but I really don't want to use a completely different method for sorting it and we're not allowed to use .sort() or .sorted() since we have to write our own sort function. Is there something I'm doing wrong?

def super_simple_sort(my_list):
switched = True
while switched:
switched = False
for i in range(len(my_list)-1):
if my_list[i] > my_list[i+1]:
my_list[i],my_list[i+1] = my_list[i+1],my_list[i]
switched = True
super_simple_sort(some_list)
print some_list
is a very simple sorting implementation ... that is equivelent to yours but takes advantage of some things to speed it up (we only need one for loop, and we only need to repeat as long as the list is out of order, also python doesnt require a temp var for swapping values)
since its changing the actual array values you actually dont even need to return

I want a function to return me the value of the equation for every number in the list. I have a list of 24 parameters, and I need to solve an equation for every value of this list.
This is the way I get my list:
wlist=[]
def w(i):
for i in range(24):
Calctruesolar=((i*60/1440)*1440+eq_time()+4*long-60*timezone)%1440
if Calctruesolar/4<0:
Calcw=(Calctruesolar/4)+180
wlist.append(Calcw)
print(Calcw)
else:
Calcw=(Calctruesolar/4)-180
wlist.append(Calcw)
print(Calcw)
Then, the list is this one:
>>> wlist=
[166.24797550450222, -178.75202449549778, -163.75202449549778, -148.75202449549778, -133.75202449549778, -118.75202449549778, -103.75202449549778, -88.75202449549778, -73.75202449549778, -58.75202449549778, -43.75202449549778, -28.75202449549778, -13.752024495497778, 1.2479755045022216, 16.24797550450222, 31.24797550450222, 46.24797550450222, 61.24797550450222, 76.24797550450222, 91.24797550450222, 106.24797550450222, 121.24797550450222, 136.24797550450222, 151.24797550450222]
Now, I use the next function:
def hourly_radiation(wlist):
for i in wlist:
Calcrt=(math.pi/24)*(a()+b()*math.cos(math.radians(i)))*((math.cos(math.radians(i)))-math.cos(math.radians(wss())))/(math.sin(math.radians(wss()))-((math.pi*wss()/180)*math.cos(math.radians(wss()))))
CalcI=Calcrt*radiation
print(Calcrt,CalcI)
So, I want to receive Calcrt and CalcI for every value inside the list. But it doesn't work. I have been looking for information in internet and tutorials but I didn't find anything.

Try this:
def hourly_radiation(wlist):
rt_list = []
I_list = []
for i in wlist:
Calcrt = (math.pi/24)*(a()+b()*math.cos(math.radians(i)))*((math.cos(math.radians(i)))-math.cos(math.radians(wss())))/(math.sin(math.radians(wss()))-((math.pi*wss()/180)*math.cos(math.radians(wss()))))
CalcI = Calcrt*radiation
rt_list.append(Calcrt)
i_list.append(CalcI)
print(Calcrt,CalcI)
dict = {}
dict["Calcrt"] = rt_list
dict["CalcI"] = i_list
return dict
This would return the values as a dictionary containing two lists. You may use any data structure that matches your requirements.
You may also create a tuple in each loop run and append it to a list and return it, like:
def hourly_radiation(wlist):
rt_list = []
data = ()
for i in wlist:
Calcrt = (math.pi/24)*(a()+b()*math.cos(math.radians(i)))*((math.cos(math.radians(i)))-math.cos(math.radians(wss())))/(math.sin(math.radians(wss()))-((math.pi*wss()/180)*math.cos(math.radians(wss()))))
CalcI = Calcrt*radiation
data = (Calcrt, CalcI)
print(Calcrt, CalcI)
rt_list.append(data)
return rt_list
I have not run or tested this code, but I hope it should work.
Please use this as a starting point and not as a copy-paste solution.

I have a script which I'm using to read an excel file and update an SQL database. I'm reading the excel file every 30 seconds using a loop. However I only want to update the database when the excel file changes
If I use the != operator when the loop cycles it refreshes the value of 'temp' and thus does not register that the value is the same.
Does anyone have an idea how to solve this problem..?
Thanks!
edit: updated to make my problem more clear!
def update():
threading.Timer(1, update).start()
book = open_workbook('bet.xls')
def odds():
sheet = book.sheet_by_name('xyz')
match_sheet = sheet.cell(5,0).value
data = book.sheet_by_name(sheet)
vv = data.cell(3,26).value
temp= None
if vv != temp:
print 'hello'
temp= vv
odds()
update()

Yes, Python built-in containers are compared by value (both tuples, lists and dicts).
Something like this (I used a list comprehension to add fanciness):
//init
pvv=None
<...>
//iteration
vv= [data.cell(i,j).value for (i,j) in ((2,26),(3,26),(4,26))]
if vv!=pvv:
//do something
pvv=vv

Using: Python 2.4
Currently, I have a nested for loop that iterates over 2 lists and makes a match based on two elements that exists on both lists. Once a match has been found, it the element from the r120Final list and puts in a new list called "r120Delta":
for r120item in r120Final:
for spectraItem in spectraFinal:
if(str(spectraItem[0]) == r120item[2].strip()) and (str(spectraItem[25]) == r120item[10]):
r120Delta.append(r120item)
break
The problem is that this is SO SLOW and the lists aren't that deep. The R120 is about 64,000 lines and the Spectra is about 150,000 lines.
The r120Final list is a nested array and it looks like so:
r120Final[0] = [['xxx','xxx','12345','xxx','xxx','xxx','xxx','xxx','xxx','xxx','234567']]
...
r120Final[n] = [['xxx','xxx','99999','xxx','xxx','xxx','xxx','xxx','xxx','xxx','678901']]
The spectraFinal list is essentially the same, a nested array and it looks like so:
spectraFinal[0] = [['12345','xxx','xxx','xxx','xxx','xxx','xxx','xxx','xxx','xxx','xxx','xxx','xxx','xxx','xxx','xxx','xxx','xxx','xxx','xxx','xxx','xxx','xxx','xxx','xxx','234567']]
...
spectraFinal[0] = [['99999','xxx','xxx','xxx','xxx','xxx','xxx','xxx','xxx','xxx','xxx','xxx','xxx','xxx','xxx','xxx','xxx','xxx','xxx','xxx','xxx','xxx','xxx','xxx','xxx','678901']]
Finally, the reason for the "r120Delta" is so that way I can then do a list differential between r120Final and r120Delta and retrieve r120 data elements that were NOT matched. This is the function I defined for this very task, and again, slow:
def listDiff( diffList, completeList ):
returnList = []
for completeItem in completeList:
if not completeItem in diffList:
returnList.append(completeItem)
return returnList
Basically, I'm knowledgeable in Python but by no means an expert. I'm looking for some experts to show me how to speed this up. Any help is appreciated!

spectra_set = set((str(spectraItem[0]), str(spectraItem[25])) for spectraItem in spectraFinal)
returnList = []
for r120item in r120Final:
if (r120item[2].strip(), r120item[10]) not in spectra_set:
returnList.append(r120item)
This will add all items that didn't match to the returnList.
You can do it in one line (if you really want) as
returnList = [r120item for r120item in r120Final
if (r120item[2].strip(), r120item[10]) not in
set((str(spectraItem[0]), str(spectraItem[25]))
for spectraItem in spectraFinal)]
If you need the full spectraItem:
spectra_dict = dict(((str(spectraItem[0]), str(spectraItem[25])), spectraItem) for spectraItem in spectraFinal)
returnList = []
for r120item in r120Final:
key = (r120item[2].strip(), r120item[10])
if key not in spectra_dict:
returnList.append(r120item)
else:
return_item = some_function_of(r120item, spectra_dict[key])
returnList.append(return_item)