How to properly set an increment in a while loop? - python-3.x

Question

I have a dataframe (DF)
I need to loop over each row and check if some conditions are met in that row
if they are then flag that row (say I add another column labeled "flag" and equalize it to 1)- in the same loop check if there are other rows that have similar conditions, if they do then flag them as well. At the next loop look at the same DF but exclude the flagged rows. The size of the DF will go from NxM to (N-n) x M where n is the number of rows flagged.
The loop will go on until the len(DF)is <=1 (meaning until all rows are flagged as 1). The for loop does not work because as the loop goes on the size of DF shrinks so I can only use while loop with increment. However, how can I set the increment ( it should be dynamic)?
I am really not sure how to tackle this problem.
Here is a failed attempt.
a=len(DF.loc[DF['flag'] != 1]) #should be (NxM) initially
i = 0
# at every loop we redefine size of DF in variable a
while a >= 1:
print(i)
# select first row
row = DF.loc[DF['flag'] != 1].iloc[[i]]
# flag row if conditions are met
DF['flag'].values[i] = np.where(if conditions met, 1, '')
#there is another piece of code that looks for rows with similar
#conditions but won't add it here
# the following variable a redefines length of DF
a=len(allHoldingsLookUp.loc[allHoldingsLookUp['flag'] != 1])
i+=1
I have a problem here. The increment I do not work. Say "i" reaches 100 and the length of DF shrinks to 70, then the code fails. The increase needs to be set differently but not sure how.
Any comments or suggestions are more than welcome.

Answer 1

Please try if this change works..
a=len(DF.loc[DF['flag'] != 1]) #should be (NxM) initially
# at every loop we redefine size of DF in variable a
while a >= 1:
i = 1
# select first row
row = DF.loc[DF['flag'] != 1].iloc[[i]]
# flag row if conditions are met
DF['flag'].values[i] = np.where(if conditions met, 1, '')
#there is another piece of code that looks for rows with similar
#conditions but won't add it here
# the following variable a redefines length of DF
try:
a=len(DF.loc[DF['flag'] != 1])
except:
break

Answer 2

Can you please try this. Hope it works.
def recur(DF):
row = DF.loc[DF['flag'] != 1].iloc[[1]]
DF['flag'].values[1] = np.where(if conditions met, 1, '')
#there is another piece of code that looks for rows with similar
#conditions but won't add it here
# the following variable a redefines length of DF
a=len(DF.loc[DF['flag'] != 1])
if a >= 1:
recur(DF.loc[DF['flag'] != 1])
return none