dummy counter
  0      1
  0      1
  0      1
  1      1
  0      1
  0      1
  1      1
  0      1
 ...    ...
  1      1
  0      1
  0      1
 ...    ...

dummy counter
  0      1
  0      1
  0      1
  1      1
  0      2
  0      3
  1      1
  0      2
 ...    ...
  1      1
  0      2
  0      3
 ...    ...

counter = False
for idx in df.index:
    if counter:
        if df.loc[idx, "var1"] > 0:
            counter = False
        else:
            df.loc[idx, "counter"] += 1
    else:
        if df.loc[idx, "var1"] < 1:
            cambiar_signo = True