[FIXED] determine the position of the variable value by counting character

Issue

I need to count the position of each variable value in the data frame. For example let's use this data frame:

Create the DataFrame

data = {
    'ol': ['H_KXKnn1_01_p_lk0', 'H_KXKnn1_02_p_lk0', 'H_KXKnn1_03_p_lk0'],
    'nl': [12.01, 89.01, 25.01],
    'nol': ['Xn', 'Ln', 'Rn'],
    'nolp': [68, 70, 72],
    'nolxx': [0.0, 1.0, 5.0]
}

df = pd.DataFrame(data)

and I am saving this data frame as .dat

df.to_csv('your_file.dat', sep='\t', index=False)

When I count the position where each value character starts and ends in the .dat file I would have:

variable position (start,end)
ol        (0,17)
nl        (18,23)
nol       (24,26)
nolp      (27,29)
nolxx     (30,33)

I am considering the "_", ".", and space as character as well. However when I run this code that iterate over each column:

for col in df.columns:
    col_length = df[col].astype(str).apply(len).max() + df[col].astype(str).apply(lambda x: x.count('_') + x.count('.')).max()
    positions[col] = (current_pos, current_pos + col_length - 1)
    current_pos += col_length + 1

positions_df = pd.DataFrame(list(positions.items()), columns=['Variable', 'Position'])

it returns the following values:

  Variable    Position
      ol      (0, 20)
      nl     (22, 27)
     nol     (29, 30)
    nolp     (32, 33)
   nolxx     (35, 38)

I am not sure why it is returning different numbers/position. Any help how I can do that is very welcome! Thank you!!

Solution

The length of all strings in first column is 17. You are adding an additional value to it that makes the result different. Since you have 3 '_''s in the string, it becomes 17 + 3 = 20.

df[col].astype(str).apply(lambda x: x.count('_') + x.count('.')

Here is the modified version of your code that produces the same output as you get from your first code :

positions = {}
current_pos = 0

for col in df.columns:
    col_length = df[col].astype(str).apply(len).max()
    positions[col] = (current_pos, current_pos + col_length)
    current_pos += col_length + 1

positions_df = pd.DataFrame(list(positions.items()), columns=['Variable', 'Position'])

And here is the output :

 Variable  Position
0       ol   (0, 17)
1       nl  (18, 23)
2      nol  (24, 26)
3     nolp  (27, 29)
4    nolxx  (30, 33)

Answered By - Mohsen_Fatemi