List of lists into numpy array

by

If your list of lists contains lists with varying number of elements then the answer of Ignacio Vazquez-Abrams will not work. Instead there are at least 3 options:

1) Make an array of arrays:

x=[[1,2],[1,2,3],[1]]
y=numpy.array([numpy.array(xi) for xi in x])
type(y)
>>><type 'numpy.ndarray'>
type(y[0])
>>><type 'numpy.ndarray'>

2) Make an array of lists:

x=[[1,2],[1,2,3],[1]]
y=numpy.array(x)
type(y)
>>><type 'numpy.ndarray'>
type(y[0])
>>><type 'list'>

3) First make the lists equal in length:

x=[[1,2],[1,2,3],[1]]
length = max(map(len, x))
y=numpy.array([xi+[None]*(length-len(xi)) for xi in x])
y
>>>array([[1, 2, None],
>>>       [1, 2, 3],
>>>       [1, None, None]], dtype=object)

More Related Contents:

  1. How to create a list of list from the given input? [closed]
  2. How to find all occurrences of an element in a list
  3. What are the advantages of NumPy over regular Python lists?
  4. Find nearest indices for one array against all values in another array – Python / NumPy
  5. Convert NumPy array to Python list
  6. What is the inverse function of zip in python? [duplicate]
  7. How to use python numpy.savetxt to write strings and float number to an ASCII file?
  8. Python Array Slice With Comma?
  9. python pandas flatten a dataframe to a list
  10. How to convert list of numpy arrays into single numpy array?
  11. List to array conversion to use ravel() function
  12. Numpy individual element access slower than for lists
  13. Filtering a list based on a list of booleans
  14. Index all *except* one item in python
  15. How to access a column in a list of lists in python
  16. How can I turn a flat list into a 2D array in python?
  17. Pythonic way to print list items
  18. Detecting consecutive integers in a list [duplicate]
  19. Interweaving two numpy arrays
  20. How can I attach a pyplot function to a figure instance?
  21. How to find the min/max value of a common key in a list of dicts?
  22. How to transform string of space-separated key,value pairs of unique words into a dict
  23. Python range() and zip() object type
  24. How do I merge multiple lists into one list? [duplicate]
  25. Easy way to test if each element in an numpy array lies between two values?
  26. Python: filtering lists by indices
  27. Python numpy: cannot convert datetime64[ns] to datetime64[D] (to use with Numba)
  28. Numpy shuffle multidimensional array by row only, keep column order unchanged
  29. Numpy array broadcasting rules
  30. Nested lambda statements when sorting lists

Leave a Comment