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other:python:misc_by_jyp [2022/02/21 16:46]
jypeter [numpy related stuff] Added reduceat
other:python:misc_by_jyp [2022/05/23 16:01]
jypeter [numpy related stuff] Changed the VIEW update warnng example
Line 39: Line 39:
 True</​code>​ True</​code>​
  
 +==== Playing with strings ====
 +
 +=== Filenames, etc... ===
 +
 +Check [[other:​python:​misc_by_jyp#​working_with_paths_and_filenames|Working with paths and filenames]] and [[other:​python:​misc_by_jyp#​generating_file_names|Generating file names]]
 +
 +=== Splitting strings ===
 +
 +It's easy to split a string with multiple blank delimiters, or a specific delimiter, but it can be harder to deal with sub-strings
 +
 +<​code>>>>​ str_with_blanks = '​one ​   two\t3\t\tFOUR'​
 +>>>​ str_with_blanks.split()
 +['​one',​ '​two',​ '​3',​ '​FOUR'​]
 +
 +>>>​ str_with_simple_delimiters = '​1,​2,​3.14, ​ 4'
 +>>>​ str_with_simple_delimiters.split(','​)
 +['​1',​ '​2',​ '​3.14',​ ' ​ 4']
 +
 +>>>​ complex_string='​-o 1 --long "A string with accented chars: é è à ç"'​
 +>>>​ complex_string.split()
 +['​-o',​ '​1',​ '​--long',​ '"​A',​ '​string',​ '​with',​ '​accented',​ '​chars:',​ '​\xc3\xa9',​ '​\xc3\xa8',​ '​\xc3\xa0',​ '​\xc3\xa7"'​]
 +
 +>>>​ import shlex
 +>>>​ shlex.split(complex_string)
 +['​-o',​ '​1',​ '​--long',​ 'A string with accented chars: \xc3\xa9 \xc3\xa8 \xc3\xa0 \xc3\xa7'​]</​code>​
 ==== Working with paths and filenames ==== ==== Working with paths and filenames ====
  
Line 222: Line 247:
  
 ==== numpy related stuff ==== ==== numpy related stuff ====
 +
 +=== Dealing with a variable number of indices ===
 +
 +[[https://​numpy.org/​doc/​stable/​user/​basics.indexing.html#​dealing-with-variable-indices|Official reference]]
 +
 +<​code>>>>​ i10 = np.identity(10)
 +>>>​ i10
 +array([[1., 0., 0., 0., 0., 0., 0., 0., 0., 0.],
 +       [0., 1., 0., 0., 0., 0., 0., 0., 0., 0.],
 +...
 +       [0., 0., 0., 0., 0., 0., 0., 0., 0., 1.]])
 +>>>​ i10.shape
 +(10, 10)
 +
 +>>>​ i10[3:7, 4:6]
 +array([[0., 0.],
 +       [1., 0.],
 +       [0., 1.],
 +       [0., 0.]])
 +       
 +>>>​ s0 = slice(3, 7)
 +>>>​ s1 = slice(4, 6)
 +>>>​ i10[s0, s1]
 +array([[0., 0.],
 +       [1., 0.],
 +       [0., 1.],
 +       [0., 0.]])
 +       
 +>>>​ my_slices = (s0, s1)
 +>>>​ i10[my_slices]
 +array([[0., 0.],
 +       [1., 0.],
 +       [0., 1.],
 +       [0., 0.]])
 +       
 +>>>​ my_fancy_slices = (s0, Ellipsis)
 +>>>​ i10[my_fancy_slices]
 +array([[0., 0., 0., 1., 0., 0., 0., 0., 0., 0.],
 +       [0., 0., 0., 0., 1., 0., 0., 0., 0., 0.],
 +       [0., 0., 0., 0., 0., 1., 0., 0., 0., 0.],
 +       [0., 0., 0., 0., 0., 0., 1., 0., 0., 0.]])
 +>>>​ i10[my_fancy_slices].shape
 +(4, 10)
 +
 +>>>​ # WARNING! DANGERRRR! NEVER forget that a VIEW is NOT A COPY
 +>>>​ # and that you can change the content of the original array by mistake
 +>>>​ my_view = i10[my_slices]
 +>>>​ my_view[:, :] = -1
 +>>>​ my_view
 +array([[-1.,​ -1.],
 +       [-1., -1.],
 +       [-1., -1.],
 +       [-1., -1.]])
 +>>>​ i10
 +array([[ 1.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.],
 +       [ 0.,  1.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.],
 +       [ 0.,  0.,  1.,  0.,  0.,  0.,  0.,  0.,  0.,  0.],
 +       [ 0.,  0.,  0.,  1., -1., -1.,  0.,  0.,  0.,  0.],
 +       [ 0.,  0.,  0.,  0., -1., -1.,  0.,  0.,  0.,  0.],
 +       [ 0.,  0.,  0.,  0., -1., -1.,  0.,  0.,  0.,  0.],
 +       [ 0.,  0.,  0.,  0., -1., -1.,  1.,  0.,  0.,  0.],
 +       [ 0.,  0.,  0.,  0.,  0.,  0.,  0.,  1.,  0.,  0.],
 +       [ 0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  1.,  0.],
 +       [ 0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  1.]])</​code>​
  
 === Finding and counting unique values === === Finding and counting unique values ===
other/python/misc_by_jyp.txt · Last modified: 2023/12/08 15:51 by jypeter