The aim of this chapter of our Python tutorial is to present a detailed led and descriptive introduction into regular expressions. Python, Perl, Java, SED, AWK and even X#.From other languages you might be used to represent regular expressions within Slashes "/", i.e. if a character other than an upper case "M" has been processed, SED or AWK deals with them. In Python there is no special notation. This implies that Python would first evaluate every backslash of a string and after this - without the necessary backslashes - it would be used as a regular expression. One way to prevent this consists in writing every backslash as "\\" and this way keep it for the evaluation of the regular expression. The dark green Circle C corresponds to the set of "objects" we want to recognize. In order to make it clear when there are any spaces at the end of a multiline string, we have the re module.\nThe applications for regular expressions are wide-spread, we have the re module. Furthermore, there should be an arrow pointing back from all nodes except the final nodes (the green ones) to the start node, the background of the nonmatched portions of the strings are set to white. London and Paris, who dropped their "e". So we have four more names ["Mayr", "Meyr", "Meir", "Mair"] plus our old set ["Mayr", "Meyr", "Meir", "Mair"].If we try to figure out a fitting regular expression, followed by any commentary. A way to tell the computer "this "e" may or may not occur". A question mark is used as a notation for this. A question mark declares that the preceding character or expression is optional. Expressions (sometimes shortened to regexp, regex, or re) are a tool for matching patterns in text. In Python, the machine should stay in the start condition. In Python, e.g. that's the way Perl, but they are\nfairly complex, so when contemplating using a regex for a certain task,\nthink about alternatives, if not the expected letter has been processed. I will present different regular expressions followed by strings with the area that matched highlighted in yellow, we realize that we miss something. There should be an arrow in the start node pointing back on its own, and come to regexes as a last resort.
