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# pandas.Series.str.replace

Series.str.replace(pat, repl, n=-1, case=None, flags=0, regex=False)

  Replace each occurrence of pattern/regex in the Series/Index.

  Equivalent to `str.replace()` or `re.sub()`, depending on the regex value.

  Parameters:
    pat str or compiled regex

      String can be a character sequence or regular expression.

    repl str or callable

      Replacement string or a callable. The callable is passed the regex match object and must return a replacement string to be used. See `re.sub()`.

    n int, default -1 (all)

      Number of replacements to make from start.

    case bool, default None

      Determines if replace is case sensitive:

      - If True, case sensitive (the default if pat is a string)

      - Set to False for case insensitive

      - Cannot be set if pat is a compiled regex.

    flags int, default 0 (no flags)

      Regex module flags, e.g. re.IGNORECASE. Cannot be set if pat is a compiled regex.

    regex bool, default False

      Determines if the passed-in pattern is a regular expression:

      - If True, assumes the passed-in pattern is a regular expression.

      - If False, treats the pattern as a literal string

      - Cannot be set to False if pat is a compiled regex or repl is a callable.

  Returns:
    Series or Index of object

      A copy of the object with all matching occurrences of pat replaced by repl.

  Raises:
    ValueError

      - if regex is False and repl is a callable or pat is a compiled regex

      - if pat is a compiled regex and case or flags is set

  Notes

  When pat is a compiled regex, all flags should be included in the compiled regex. Use of case, flags, or regex=False with a compiled regex will raise an error.

  Examples

  When pat is a string and regex is True, the given pat is compiled as a regex. When repl is a string, it replaces matching regex patterns as with `re.sub()`. NaN value(s) in the Series are left as is:

      >>> pd.Series(['foo', 'fuz', np.nan]).str.replace('f.', 'ba', regex=True)
      0    bao
      1    baz
      2    NaN
      dtype: object

  When pat is a string and regex is False, every pat is replaced with repl as with `str.replace()`:

      >>> pd.Series(['f.o', 'fuz', np.nan]).str.replace('f.', 'ba', regex=False)
      0    bao
      1    fuz
      2    NaN
      dtype: object

  When repl is a callable, it is called on every pat using `re.sub()`. The callable should expect one positional argument (a regex object) and return a string.

  To get the idea:

      >>> pd.Series(['foo', 'fuz', np.nan]).str.replace('f', repr, regex=True)
      0    <re.Match object; span=(0, 1), match='f'>oo
      1    <re.Match object; span=(0, 1), match='f'>uz
      2                                            NaN
      dtype: object

  Reverse every lowercase alphabetic word:

      >>> repl = lambda m: m.group(0)[::-1]
      >>> ser = pd.Series(['foo 123', 'bar baz', np.nan])
      >>> ser.str.replace(r'[a-z]+', repl, regex=True)
      0    oof 123
      1    rab zab
      2        NaN
      dtype: object

  Using regex groups (extract second group and swap case):

      >>> pat = r"(?P<one>\w+) (?P<two>\w+) (?P<three>\w+)"
      >>> repl = lambda m: m.group('two').swapcase()
      >>> ser = pd.Series(['One Two Three', 'Foo Bar Baz'])
      >>> ser.str.replace(pat, repl, regex=True)
      0    tWO
      1    bAR
      dtype: object

  Using a compiled regex with flags

      >>> import re
      >>> regex_pat = re.compile(r'FUZ', flags=re.IGNORECASE)
      >>> pd.Series(['foo', 'fuz', np.nan]).str.replace(regex_pat, 'bar', regex=True)
      0    foo
      1    bar
      2    NaN
      dtype: object