python13():
  Exercises for reading and writing files.

  Use np.savetxt() to write an array to a text file.

  Created the text file "hilbert_matrix.txt"

  Use np.loadtxt() to read a table of data from a text file.

The table in "hilbert_matrix.txt" has 5 rows and 5 columns.
The maximum entries in each column:
[1.         0.5        0.33333333 0.25       0.2       ]

  Use open(), .write(), and .close() to create a text file.

  Wrote the text file "mystery.txt"

  Use open(), .write(), and .close() to read a text file.

  Contents of "mystery.txt"

Yesterday, upon the stair,
I met a man who wasn't there.
He wasn't there again today
I wish, I wish he'd go away.

  Use the append mode in open() to add lines to an existing file.

  More lines were added to "mystery.txt"

  Use .split() to read words from lines from text file.

  Wrote the text file "patient.txt"

Alice 60 120.3 23.500784819267995
Bob 65 200.5 33.37389560132733
Carol 70 160.1 22.978119901663018

  Write data of irregular length

  Created file"slap_matrix.txt"

  Carefully read lines of varying length and meaning.