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Say you want to find a phone number in a string. You know the pattern: three numbers, a hyphen, three numbers, a hyphen, and four numbers. Here's an example: 415-555-4242. Let's use a function named isPhoneNumber() to check whether a string matches this pattern, returning either True or False. Open a new file editor window and save the file as isPhone Number.py. Regular expressions, called regexes for short, are descriptions for a pattern of text. For example, a \d in a regex stands for a digit character that is, any single numeral 0 to 9. The regex \d\d\d-\d\d\d- \d\d\d\d is used by Python to match the text containing phone numbers in the isPhone Number() function: a string of three numbers, a hyphen, three more numbers, another hyphen, and four numbers. Any other string would not match the \d\d\d-\d\d\d-\d\d \d\d regex. But regular expressions can be much more sophisticated. For example, adding a 3 in curly brackets ({3}) after a pattern is like saying, "Match this pattern three times." So the slightly shorter regex \d{3}-\d{3}-\d{4} also matches the correct phone number format. All the regex functions in Python are in the re module. Enter the following into an interactive shell to import this module: >>> import re A Regex object's search() method searches the string it is passed for any matches to the regex. The search() method will return None if the regex pattern is not found in the string. If the pattern is found, the search() method returns a Match object. Match objects have a group() method that will return the actual matched text from the searched string.

Say you want to find a phone number in a string. You know the pattern: three numbers, a hyphen, three numbers, a hyphen, and four numbers. Here's an example: 415-555-4242. Let's use a function named isPhoneNumber() to check whether a string matches this pattern, returning either True or False. Open a new file editor window and save the file as isPhone Number.py. Regular expressions, called regexes for short, are descriptions for a pattern of text. For example, a \d in a regex stands for a digit character that is, any single numeral 0 to 9. The regex \d\d\d-\d\d\d- \d\d\d\d is used by Python to match the text containing phone numbers in the isPhone Number() function: a string of three numbers, a hyphen, three more numbers, another hyphen, and four numbers. Any other string would not match the \d\d\d-\d\d\d-\d\d \d\d regex. But regular expressions can be much more sophisticated. For example, adding a 3 in curly brackets ({3}) after a pattern is like saying, "Match this pattern three times." So the slightly shorter regex \d{3}-\d{3}-\d{4} also matches the correct phone number format. All the regex functions in Python are in the re module. Enter the following into an interactive shell to import this module: >>> import re A Regex object's search() method searches the string it is passed for any matches to the regex. The search() method will return None if the regex pattern is not found in the string. If the pattern is found, the search() method returns a Match object. Match objects have a group() method that will return the actual matched text from the searched string.

Database System Concepts
Database System Concepts
7th Edition
ISBN:9780078022159
Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Chapter1: Introduction
Section: Chapter Questions
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### How to Find a Phone Number in a String Using Python Say you want to find a phone number in a string. You know the pattern: three numbers, a hyphen, three numbers, a hyphen, and four numbers. Here’s an example: 415-555-4242. #### Checking a String with isPhoneNumber() Function Let’s use a function named `isPhoneNumber()` to check whether a string matches this pattern, returning either True or False. Open a new file editor window and save the file as `isPhoneNumber.py`. #### Understanding Regular Expressions Regular expressions, called regexes for short, are descriptions for a pattern of text. For example, a `\d` in a regex stands for a digit character—that is, any single numeral 0 to 9. The regex `\d\d\d-\d\d\d-\d\d\d\d` is used by Python to match text containing phone numbers in the `isPhoneNumber()` function: a string of three numbers, a hyphen, three more numbers, another hyphen, and four numbers. Any other string would not match the `\d\d\d-\d\d\d-\d\d\d\d` regex. But regular expressions can be much more sophisticated. For example, adding a 3 in curly brackets (`{3}`) after a pattern is like saying, “Match this pattern three times.” So the slightly shorter regex `\d{3}-\d{3}-\d{4}` also matches the correct phone number format. #### Using Regex Functions in Python All the regex functions in Python are in the `re` module. Enter the following into an interactive shell to import this module: ```python >>> import re ``` #### Using the search() Method A Regex object’s `search()` method searches the string it is passed for any matches to the regex. The `search()` method will return None if the regex pattern is not found in the string. If the pattern is found, the `search()` method returns a Match object. Match objects have a `group()` method that will return the actual matched text from the searched string. This fundamental understanding of regex can help you efficiently find patterns such as phone numbers in strings using Python.
Transcribed Image Text:### How to Find a Phone Number in a String Using Python Say you want to find a phone number in a string. You know the pattern: three numbers, a hyphen, three numbers, a hyphen, and four numbers. Here’s an example: 415-555-4242. #### Checking a String with isPhoneNumber() Function Let’s use a function named `isPhoneNumber()` to check whether a string matches this pattern, returning either True or False. Open a new file editor window and save the file as `isPhoneNumber.py`. #### Understanding Regular Expressions Regular expressions, called regexes for short, are descriptions for a pattern of text. For example, a `\d` in a regex stands for a digit character—that is, any single numeral 0 to 9. The regex `\d\d\d-\d\d\d-\d\d\d\d` is used by Python to match text containing phone numbers in the `isPhoneNumber()` function: a string of three numbers, a hyphen, three more numbers, another hyphen, and four numbers. Any other string would not match the `\d\d\d-\d\d\d-\d\d\d\d` regex. But regular expressions can be much more sophisticated. For example, adding a 3 in curly brackets (`{3}`) after a pattern is like saying, “Match this pattern three times.” So the slightly shorter regex `\d{3}-\d{3}-\d{4}` also matches the correct phone number format. #### Using Regex Functions in Python All the regex functions in Python are in the `re` module. Enter the following into an interactive shell to import this module: ```python >>> import re ``` #### Using the search() Method A Regex object’s `search()` method searches the string it is passed for any matches to the regex. The `search()` method will return None if the regex pattern is not found in the string. If the pattern is found, the `search()` method returns a Match object. Match objects have a `group()` method that will return the actual matched text from the searched string. This fundamental understanding of regex can help you efficiently find patterns such as phone numbers in strings using Python.
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