How to get length of a list of lists in python

Question

So  if I have a list called myList I use len myList  to find the number of elements in that list  Fine  But how do I find the number of lists in a list   text   open  filetest txt    r   myLines   text readlines   numLines len myLines  print numLines   The above text file used has 3 lines of 4 elements separated by commas  The variable numLines prints out as  4  not  3   So  len myLines  is returning the number of elements in each list not the length of the list of lists   When I print myLines 0  I get the first list  myLines 1  the second list  etc  But len myLines  does not show me the number of lists  which should be the same as  number of lines    I need to determine how many lines are being read from the file

User · Answer

You can do it with reduce   a     1  2  3    4  5  6    7  8  9        1  2   print reduce lambda count  l  count   len l   a  0     result is 11

User · Answer

This saves the data in a list of lists   text   open  filetest txt    r   data       for line in text      data append  line strip   split      print  number of lines    len data  print  number of columns    len data 0    print  element in first row column two    data 0  1

User · Answer

The method len   returns the number of elements in the list    list1  list2    123   xyz    zara     456   abc       print  First list length      len list1      print  Second list length      len list2    When we run above program  it produces the following result -  First list length    3 Second list length    2

User · Answer

if the name of your list is listlen then just type len listlen   This will return the size of your list in the python

User · Answer

The above text file used has 3 lines of 4 elements separated by commas  The variable numLines prints out as  4  not  3   So  len myLines  is returning the number of elements in each list not the length of the list of lists    It sounds like you re reading in a  csv with 3 rows and 4 columns  If this is the case  you can find the number of rows and lines by using the  split   method   text   open  filetest txt    r   read   myRows   text split   n         this method tells Python to split your filetest object each time it encounters a line break  print len myRows                will tell you how many rows you have for row in myRows    myColumns   row split         this method will consider each of your rows one at a time  For each of those rows  it will split that row each time it encounters a comma      print len myColumns           will tell you  for each of your rows  how many columns that row contains

[python] How to get length of a list of lists in python

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