title: Importing a CSV file into lists of lists without using modules
body: <p>I'm a beginner and I am stuck at this practice exercise. I am not allowed to use any modules to solve this problem.
  I have a csv file with 10 rows representing a different house in each row and 20 columns representing days. For each day, it was recorded whether the temperature in a house fell below 15 deg C. There is no header to the file.</p>
  <p>0,2,4,1,1,2,...<br />
  2,2,2,1,1,0,...<br />
  1,1,1,2,0,0,...<br />
  ...</p>
  <p>I need to perform some calculations such as the average number of times the temp fell below 15 deg C per house and per day. So I'm thinking I need a list of houses which contains all the rows as lists and a list of days which contains sorted values of the correlative columns like [[0,2,1,...],[2,2,1,...],...] to perform these calculations. So far I have tried</p>
  <pre><code>file = open(&quot;filename.csv&quot;)
  days = []
  for line in file:
      line = line.strip()
      data = line.split(&quot;,&quot;)
      for x in range(0, len(data)):
          days.append(int(data[x]))
  print(days)
  </code></pre>
  <p>This is not giving me the list of days like I hoped for. I am getting one big list with all the data in it. What am I doing wrong?</p>