RegEx Exercise #3: Find the Numbers

Write five regular expressions:

• One called integers that will match all whole numbers, positive or negative.
• One called floats that will match all decimal numbers, positive or negative.
• One called positive that will match all positive numbers, whole or decimal.
• One called negative that will match all negative numbers, whole or decimal.
• One called numbers that will match all numbers, whole or decimal, positive or negative.

Details to take into account:

• Fractions of 1 may or may not be preceded by a 0. All 0.5, .5, -.5 and are valid numbers.
• Floats will have at least one decimal number. Both 4. and -3. are not valid numbers.
• Positives numbers may or may not be preceded by a +. Both 3 and +3 are valid numbers.
• Numbers preceded by more than one symbol or having more than one decimal point are no considered valid. All ++1, -+4, 3.3.6 are not valid numbers.
• All numbers, valid or not, will be preceded and followed by a whitespace.

Example

txt = " 123.456 2 +7 -88 -.25 9.10.11 -4. +-34 -0.6 --5 "
integers = "yourregularexpressionhere"
floats = "yourregularexpressionhere"
positive = "yourregularexpressionhere"
negative = "yourregularexpressionhere"
numbers = "yourregularexpressionhere"

re.findall(integers, txt) ➞ ["2", "+7", "-88"]
re.findall(floats, txt) ➞ ["123.456", "-.25", "-0.6"]
re.findall(positive, txt) ➞ ["123.456", "2", "+7"]
re.findall(negative, txt) ➞ ["-88", "-.25", "-0.6"]
re.findall(numbers, txt) ➞ ["123.456", "2", "+7", "-88", "-.25", "-0.6"]

Notes

• You don't need to write a function, just the pattern.

• Do not remove import re from the code.

• If you get stuck, check Comments for some helpful hints.

• You can find all the challenges of this series in my Basic RegEx collection.