d=[]
for line in f:
    words=line.split()
    numberD=float(words[0])
    d.append(numberD)

>>> s='0,0011'
>>> float(s)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: could not convert string to float: '0,0011'
>>> ns = s.replace(',', '.')
>>> ns
'0.0011'
>>> float(ns)
0.0011
>>> float(s.replace(',', '.'))
0.0011