python - Referencing Rows in Instance Variable -

apologies if answered elsewhere, cannot find (or maybe understand) appears trying do...

i have large-ish file approx. 60000 rows , 136 columns. want extract 20 columns , have created instance variable store data. data gets parsed , cut according entries in several of columns , moved new copies of instance variable maintain consistency. @ moment doing each column in instance , copy whole row @ time, cannot find way of referencing row in instance variable. examples of doing , below.

if either point me in right direction or suggest better method of doing same thing (instead of using instance variable), grateful.

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instance variable:

class instance_object:  ###------------------------------------------------------------------ ### __init__ function create object ###  ###          stores interesting parameters data  ###------------------------------------------------------------------  def __init__(self):      self.a = []     self.b = []     self.c = []     # etc 

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current main code:

result = pyf.open(datapath+data_filename) header = result[1].header file_data = result[1].data  data_a, data_b = instance_object(), instance_object()  data_a.a = file_data.var1 data_a.b = file_data.var2 data_a.c = file_data.var3 #(etc)  in range(len(data_a.a)):     if 0.0 <= data_a.a[i] <= 100.0:          if -1.0 <= data_a.b[i] <= 1.0:             data_b.a.append(data_a.a[i])             data_b.b.append(data_a.b[i])             data_b.c.append(data_a.c[i])             # etc 

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what do:

for in range(len(data_a.a)):     if 0.0 <= data_a.a[i] <= 100.0:          if -1.0 <= data_a.b[i] <= 1.0:             data_b.append(data_a[i])             # i.e. append entire row data_a data_b whilst              # maintaining structure 

instead of storing columns of data, store list of rows.

instead of storing columns, picking desired columns, filtering desired rows, can combined operations:

def file_to_rows(fname, line_to_row=none, row_filter=none, skip_header=false, mode="r"):     line_to_row |= lambda line: line     row_filter  |= lambda row:  true      open(fname, mode) inf:         line in inf:             row = line_to_row(line)             if row_filter(row):                 yield row  def line_to_row_items(items):     max_split = max(items) + 1     def fn(line):         row = line.split(none, max_split)         return [row[item] item in items]     return fn  def row_filter(row):     return (              0. <= row[0] <= 100.         , -1. <= row[1] <=   1.     )  data = list(file_to_rows(     "mydata.txt",     line_to_row_items([0, 1, 4, 5, 6, 9, 10, 15, 18, 21]),   # columns keep     skip_header = true ))