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Python Regular Expressions (regex): Forming a Regular Expression in Python


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"I never metacharacter I didn't like."

As the saying goes, "I never metacharacter I didn't like." Once you learn how to use metacharacters, you will wonder how you ever got on without them. This is particularly true in Python. Python has a robust regular expression engine and employs a wide array of metacharacters. The following is a list of the symbols and their uses:

  • .: any character except a newline.
  • ^: the boundary at the beginning of a character string (the green line)
  • $: the boundary at the end of a character string (the other green line)
  • *: zero or more instances of a pattern
  • +: one or more instances of a pattern
  • ?: one or more instances of a pattern
  • \: the indicator of an escape sequence
  • {}: used to specify parameters for the matching of the regular expression
  • []: indicates a set of characters for a single position in the regex
  • (): used to group regular expressions
  • |: used as an 'or' between two possible matches.
These are the extended alphabet of regular expression formulation. Many of them are a simple 1-to-1 symbolic meaning (".", "^", "$", "*", "+", "?", "|", "()" and "[]"). But two take on a life of their own when placed in conjunction with certain letters of the alphabet. In the next section, we will look at these compound symbols and their meanings.

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