# 8.6. Syntax Quantifier¶

• Quantifier specifies how many occurrences of preceding qualifier or identifier

• Exact

• Greedy

• Lazy

>>> import re
>>> TEXT = 'Mark Watney of Ares 3 landed on Mars on: Nov 7th, 2035 at 1:37 pm'

>>> re.findall(r'\d', TEXT)
['3', '7', '2', '0', '3', '5', '1', '3', '7']

>>> re.findall(r'\d\d\d\d', TEXT)
['2035']


## 8.6.1. Exact¶

• Exact match

• {n} - exactly n repetitions, prefer longer

>>> TEXT = 'Mark Watney of Ares 3 landed on Mars on: Nov 7th, 2035 at 1:37 pm'

>>> re.findall(r'[0-9]{2}', TEXT)
['20', '35', '37']

>>> re.findall(r'\d{2}', TEXT)
['20', '35', '37']


## 8.6.2. Greedy¶

• Prefer longest matches

• Works better with numbers

• Not that good results for text

• Default behavior

• {,n} - maximum n repetitions, prefer longer

• {n,} - minimum n repetitions, prefer longer

• {n,m} - minimum n repetitions, maximum m times, prefer longer

• * - minimum 0 repetitions, no maximum, prefer longer (alias to {0,})

• + - minimum 1 repetitions, no maximum, prefer longer (alias to {1,})

• ? - minimum 0 repetitions, maximum 1 repetitions, prefer longer (alias to {0,1})

>>> TEXT = 'Mark Watney of Ares 3 landed on Mars on: Nov 7th, 2035 at 1:37 pm'

>>> re.findall(r'\d{2,4}', TEXT)
['2035', '37']


## 8.6.3. Lazy¶

• Prefer shortest matches

• Works better with text

• Not that good results for numbers

• Non-greedy

• {,n}? - maximum n repetitions, prefer shorter

• {n,}? - minimum n repetitions, prefer shorter

• {n,m}? - minimum n repetitions, maximum m times, prefer shorter

• *? - minimum 0 repetitions, no maximum, prefer shorter (alias to {0,}?)

• +? - minimum 1 repetitions, no maximum, prefer shorter (alias to {1,}?)

• ?? - minimum 0 repetitions, maximum 1 repetition, prefer shorter (alias to {0,1}?)

>>> TEXT = 'Mark Watney of Ares 3 landed on Mars on: Nov 7th, 2035 at 1:37 pm'

>>> re.findall(r'\d{2,4}?', TEXT)
['20', '35', '37']


## 8.6.4. Greedy vs. Lazy¶

>>> TEXT = 'Mark Watney of Ares 3 landed on Mars on: Nov 7th, 2035 at 1:37 pm'

>>> re.findall(r'\d{2,4}', TEXT)  # Greedy
['2035', '37']

>>> re.findall(r'\d{2,4}?', TEXT)  # Lazy
['20', '35', '37']


Greedy vs Lazy in exact match has no difference:

>>> re.findall('\d{2}?', TEXT)
['20', '35', '37']

>>> re.findall('\d{2}', TEXT)
['20', '35', '37']


## 8.6.5. Special¶

>>> TEXT = 'Mark Watney of Ares 3 landed on Mars on: Nov 7th, 2035 at 1:37 pm'

>>> re.findall('\d{0,}', TEXT) == re.findall('\d*', TEXT)
True

>>> re.findall('\d{1,}', TEXT) == re.findall('\d+', TEXT)
True

>>> re.findall('\d+', TEXT)
['3', '7', '2035', '1', '37']

>>> re.findall('\d*', TEXT)
['', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '',
'', '', '3', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '',
'', '', '', '', '', '', '', '', '', '7', '', '', '', '', '2035', '', '',
'', '', '1', '', '37', '', '', '', '']


## 8.6.6. Examples¶

• [0-9]{2} - exactly two digits from 0 to 9

• \d{2} - exactly two digits from 0 to 9

• [A-Z]{2,10} - two to ten uppercase letters from A to Z

• [A-Z]{2-10}-[0-9]{,5} - two to ten uppercase letters from A to Z followed by dash (-) and at least five numbers

• [a-z]+ - at least one lowercase letter from a to z, but try to fit the longest match

• \d+ - number

• \d+\.\d+ - float

## 8.6.7. Use Case - 0x01¶

• Float

>>> import re
>>> TEXT = 'Pi number is 3.1415...'

>>> pi = re.findall('\d+\.\d+', TEXT)
>>> pi
['3.1415']


## 8.6.8. Use Case - 0x02¶

• Time

>>> import re
>>> TEXT = 'Mark Watney of Ares 3 landed on Mars on: Nov 7th, 2035 at 1:37 pm'

>>> re.findall('\d\d:\d\d', TEXT)
[]

>>> re.findall('\d\d?:\d\d', TEXT)
['1:37']


## 8.6.9. Use Case - 0x03¶

• Date

>>> import re
>>> from datetime import datetime

>>> TEXT = 'Mark Watney of Ares 3 landed on Mars on: Nov 7th, 2035 at 1:37 pm'
>>>
>>> result = re.findall('\w{3} \d{1,2}th, \d{4}', TEXT)

>>> result
['Nov 7th, 2035']

>>> datetime.strptime(result[0], '%b %dth, %Y').date()
datetime.date(2035, 11, 7)


## 8.6.10. Use Case - 0x04¶

>>> import re

>>> line = 'value=123'
>>>
>>> re.findall(r'(\w+)\s?=\s?(\d+)', line)
[('value', '123')]

>>> line = 'value = 123'
>>>
>>> re.findall(r'(\w+)\s?=\s?(\d+)', line)
[('value', '123')]


## 8.6.11. Use Case - 0x05¶

>>> import re
>>> HTML = '<h1>Header 1</h1><p>Paragraph 1</p><p>Paragraph 2</p>'

>>> re.findall('<p>.*</p>', HTML)
['<p>Paragraph 1</p><p>Paragraph 2</p>']

>>> re.findall('<p>.*?</p>', HTML)
['<p>Paragraph 1</p>', '<p>Paragraph 2</p>']


## 8.6.12. Use Case - 0x06¶

>>> import re
>>> HTML = '<h1>Header 1</h1><p>Paragraph 1</p><p>Paragraph 2</p>'

>>> re.findall('<p>', HTML)
['<p>', '<p>']

>>> re.findall('</p>', HTML)
['</p>', '</p>']

>>> re.findall('</?p>', HTML)
['<p>', '</p>', '<p>', '</p>']


## 8.6.13. Use Case - 0x07¶

>>> import re
>>> HTML = '<h1>Header 1</h1><p>Paragraph 1</p><p>Paragraph 2</p>'

>>> re.findall('<.+>', HTML)

>>> re.findall('<.+?>', HTML)
['<h1>', '</h1>', '<p>', '</p>', '<p>', '</p>']

>>> re.findall('</?.+?>', HTML)
['<h1>', '</h1>', '<p>', '</p>', '<p>', '</p>']

>>> re.findall('</?(.+?)>', HTML)
['h1', 'h1', 'p', 'p', 'p', 'p']

>>> tags = re.findall('</?(.+?)>', HTML)
>>> sorted(set(tags))
['h1', 'p']


## 8.6.14. Use Case - 0x08¶

>>> import re
>>> HTML = '<h1>Header 1</h1><p>Paragraph 1</p><p>Paragraph 2</p>'

>>> re.findall('</?.*>', HTML)

>>> re.findall('</?.*?>', HTML)