dictionary - Python - dict weird dict writing/reading error

Question

I have a problem reading the data from a dictionary I created to save data reconstructed by a function...

The dictionary is written whenever the value of Amp and t is reconstructed, in the loop col. At each row loop, the dictionary is saved in a list.

Part of the code where the dictionary is written:

def OptimalFilter(inNoiseMatrix, inSi, inGsig, inDgSig):
   AmpTime = Verif = dict()
   ListData = []
   for row in range(0,1000):
       for col in range(0,9):
           ...
           ...
           Amp = mm(aCoef.T,Si)
           t   = mm(bCoef.T,Si)/mm(aCoef.T,Si)
           AmpTime.update({'E_Cell_'+str(col+1): Amp, 't_Cell_'+str(col+1): t})
       ListData.append(AmpTime) 
    return ListData

I checked the reconstruction by printing the Amp and t values and they are correct. The problem occurs when I process the list data that the function returns. When I choose a key from the millionaire and iterate in the lists the value is the same:

AmpTimeXTvalid = OptimalFilter(Noise[3000:], XTvalid, gSig[3000:], DgSig[3000:])

for i in range(20):
    print(AmpTimeXTvalid[i]['E_Cell_1'])
9975.71782251447
9975.71782251447
9975.71782251447
9975.71782251447
9975.71782251447
9975.71782251447
9975.71782251447
9975.71782251447
9975.71782251447
9975.71782251447
9975.71782251447
9975.71782251447
9975.71782251447
9975.71782251447

What did I do wrong in writing/reading the dictionary?

question from:https://stackoverflow.com/questions/66056931/python-dict-weird-dict-writing-reading-error

Answer 1

You keep using the same dict object again and again, so in the end all you see is the value of last iteration. You should get a new dict inside the loop and then append it in your ListData. See below.

def OptimalFilter(inNoiseMatrix, inSi, inGsig, inDgSig):
   ListData = []
   for row in range(0,1000):
       for col in range(0,9):
           ...
           ...
           Amp = mm(aCoef.T,Si)
           t   = mm(bCoef.T,Si)/mm(aCoef.T,Si)
           AmpTime = Verif = dict() # GET A DICT EVERYTIME, OTHERWISE ALL YOU DO IS MODIFY THE SAME OBJECT AND APPEND IT ONE MORE TIME.
           AmpTime.update({'E_Cell_'+str(col+1): Amp, 't_Cell_'+str(col+1): t})
       ListData.append(AmpTime) 
    return ListData