8.12.2 Replacing Substrings and Splitting Strings

  • sub function replaces patterns in a string
  • split function breaks a string into pieces, based on patterns

Function sub—Replacing Patterns

  • sub function replaces all occurrences of a pattern with the replacement text you specify
In [109]:
import re
In [110]:
re.sub(r'\t', ', ', '1\t2\t3\t4')
Out[110]:
'1, 2, 3, 4'
  • Three required arguments:
    • the pattern to match (the tab character '\t')
    • the replacement text (', ') and
    • the string to be searched ('1\t2\t3\t4')
  • Keyword argument count can be used to specify the maximum number of replacements
In [111]:
re.sub(r'\t', ', ', '1\t2\t3\t4', count=2)
Out[111]:
'1, 2, 3\t4'

Function split

  • split function tokenizes a string, using a regular expression to specify the delimiter
  • Returns a list of strings
In [112]:
re.split(r',\s*', '1,  2,  3,4,    5,6,7,8')
Out[112]:
['1', '2', '3', '4', '5', '6', '7', '8']
  • Keyword argument maxsplit specifies maximum number of splits
In [113]:
re.split(r',\s*', '1,  2,  3,4,    5,6,7,8', maxsplit=3)
Out[113]:
['1', '2', '3', '4,    5,6,7,8']

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