Python выдает ошибку: AttributeError: 'NoneType' object has no attribute 'append'

print(fr)
with open(faylnomi,"w") as fayl:
fayl.write(fr)
b = 0
k = []
p = {}
while str(len(fr)) != 1:
fr = float(fr)
fr/=2
b+=1
if int(fr*10)%10 == 5:
k= k.append(b)
fr = fr-0.5
fr = f"{fr}"
if len(fr) == 1:
p["b"]=b
p["s"]=fr
p["k"]=k
break
with open(faylnomi,"w") as f:
f.write(str(p)+"\n#Форматированна !!!")