how do i loop over values within a for loop in python?

Question

I have a df

    1   1   2   2
    2   2   1   1

I have written a function which:

takes the df in a for loop,
adds row(s) with a default value
replaces the values with another value in randomly selected cols
writes to csv

This is my code:

def add_x(df, max):
    gt_w_x = df.copy()
    counter = 0


    for i in range(1, max):
        if len(gt_w_x) != max:
            counter+=1
            # add new row with default value
            gt_w_x.loc[-1,:] = 1
        
            # reset index
            gt_w_x = gt_w_x.reset_index(drop=True)
        
            # how to loop over these values for x ??
            x = 1
            #x = 2
        
            # assign value 'X' to x randomly selected cols on last row 
            gt_w_x.iloc[-1:, random.sample(list(range(gt_w_x.shape[1])), x)] = 'X'
        
            x = str(x)
            n = str(counter)
        
            # write to file
            df_path = 'test/' + x + '_' + n + '.csv'
            gt_w_x.to_csv(df_path) 

max = 4
add_x(df, max)

The output on my system is

test/1_1.csv  
test/1_2.csv  


cat test/1_1.csv    
0,1.0,1.0,2.0,2.0  
1,2.0,2.0,1.0,1.0  
2,1.0,X,1.0,1.0  


cat test/1_2.csv  
0,1.0,1.0,2.0,2.0  
1,2.0,2.0,1.0,1.0  
2,1.0,X,1.0,1.0  
3,1.0,X,1.0,1.0

How do I loop over values for x? The desired output for x = 1 and x = 2 is

test/1_1.csv  
test/1_2.csv  
test/2_1.csv    
test/2_2.csv

Currently, I run the function by commenting out different values for x which is suboptimal.

I don't understand why there is a question here. "How do I loop over values for x?" Well, do you see how the code already loops over values for i? Did you try doing the same thing? — Karl Knechtel
– Karl Knechtel, Commented Nov 12, 2022 at 1:15

TomerG · Accepted Answer · 2022-11-10 20:15:01Z

1

You can use a nested for loop. It works just like the one you have at the beginning of the function:

def add_x(df, max):
    for x in range(1,3):
        gt_w_x = df.copy()
        counter = 0

        for i in range(1, max):
            if len(gt_w_x) != max:
                counter+=1
                # add new row with default value
                gt_w_x.loc[-1,:] = 1

                # reset index
                gt_w_x = gt_w_x.reset_index(drop=True)

                # assign value 'X' to x randomly selected cols on last row
                gt_w_x.iloc[-1:, random.sample(list(range(gt_w_x.shape[1])), x)] = 'X'

                n = str(counter)

                # write to file
                df_path = 'test/' + str(x) + '_' + n + '.csv'
                gt_w_x.to_csv(df_path)

max = 4
add_x(df, max)

edited Nov 10, 2022 at 20:15

answered Nov 10, 2022 at 13:54

TomerG

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2 Comments

peter_parker Over a year ago

This does not appear to give the right output. In the file test/1_2.csv there are two rows containing X, which is correct. However, the first of these X-containing rows has X in three columns and the second X-containing row has X in one column. Maybe I'm missing something. Would you be willing to check?

TomerG Over a year ago

Hi @peter_parker, I updated the looping order for x and inlined the relevant str(x) function so it won't change x mid-loop.

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