How to read a text file into a list or an array with Python

Question

I am trying to read the lines of a text file into a list or array in python   I just need to be able to individually access any item in the list or array after it is created   The text file is formatted as follows   0 0 200 0 53 1 0 255     0    Where the     is above  there actual text file has hundreds or thousands more items   I m using the following code to try to read the file into a list   text file   open  filename dat    r   lines   text file readlines   print lines print len lines  text file close     The output I get is     0 0 200 0 53 1 0 255     0    1   Apparently it is reading the entire file into a list of just one item  rather than a list of individual items   What am I doing wrong

User · Answer

You can also use numpy loadtxt like  from numpy import loadtxt lines   loadtxt  filename dat   comments      delimiter      unpack False

User · Answer

This question is asking how to read the comma-separated value contents from a file into an iterable list    0 0 200 0 53 1 0 255     0   The easiest way to do this is with the csv module as follows   import csv with open  filename dat   newline     as csvfile      spamreader   csv reader csvfile  delimiter        Now  you can easily iterate over spamreader like this   for row in spamreader      print      join row     See documentation for more examples

User · Answer

You will have to split your string into a list of values using split   So  lines   text file read   split       EDIT  I didn t realise there would be so much traction to this  Here s a more idiomatic approach  import csv with open  filename csv    r   as fd      reader   csv reader fd      for row in reader            do something

User · Answer

So you want to create a list of lists    We need to start with an empty list  list of lists        next  we read the file content  line by line  with open  data   as f      for line in f          inner list    elt strip   for elt in line split                 in alternative  if you need to use the file content as numbers           inner list    int elt strip    for elt in line split               list of lists append inner list    A common use case is that of columnar data  but our units of storage are the rows of the file  that we have read one by one  so you may want to transpose your list of lists   This can be done with the following idiom  by cols   zip  list of lists    Another common use is to give a name to each column  col names     apples sold    pears sold    apples revenue    pears revenue   by names      for i  col name in enumerate col names       by names col name    by cols i    so that you can operate on homogeneous data items   mean apple prices    money fruits for money  fruits in                      zip by names  apples revenue    by names  apples sold       Most of what I ve written can be speeded up using the csv module  from the standard library   Another third party module is pandas  that lets you automate most aspects of a typical data analysis  but has a number of dependencies      Update While in Python 2 zip  list of lists  returns a different  transposed  list of lists  in Python 3 the situation has changed and zip  list of lists  returns a zip object that is not subscriptable   If you need indexed access you can use  by cols   list zip  list of lists     that gives you a list of lists in both versions of Python   On the other hand  if you don t need indexed access and what you want is just to build a dictionary indexed by column names  a zip object is just fine     file   open  some data csv   names   get names next file   columns   zip    x strip   for x in line split       for line in file    d      for name  column in zip names  columns   d name    column

[python] How to read a text file into a list or an array with Python

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