A single number from one per line in Python

Question

I have strings containing numbers with their units, for example. 2 GB, 17 feet, etc. I would like to separate the number from the block and create two different lines. Sometimes there is a space between them (for example, 2 GB), and this is easy to do with split ('').

When they are together (for example, 2 GB), I will test each character until I find a letter instead of a number.

s='17GB' number='' unit='' for c in s: if c.isdigit(): number+=c else: unit+=c 

Is there a better way to do this?

thanks

Answer 1

 s='17GB' for i,c in enumerate(s): if not c.isdigit(): break number=int(s[:i]) unit=s[i:] 

Answer 2

You can exit the loop when you find the first non-digital character

 for i,c in enumerate(s): if not c.isdigit(): break number = s[:i] unit = s[i:].lstrip() 

If you have negative and decimal numbers:

 numeric = '0123456789-.' for i,c in enumerate(s): if c not in numeric: break number = s[:i] unit = s[i:].lstrip() 

Answer 3

You can use regex to split a string into groups:

 >>> import re >>> p = re.compile('(\d+)\s*(\w+)') >>> p.match('2GB').groups() ('2', 'GB') >>> p.match('17 ft').groups() ('17', 'ft') 

Answer 4

tokenize can help:

 >>> import StringIO >>> s = StringIO.StringIO('27GB') >>> for token in tokenize.generate_tokens(s.readline): ... print token ... (2, '27', (1, 0), (1, 2), '27GB') (1, 'GB', (1, 2), (1, 4), '27GB') (0, '', (2, 0), (2, 0), '') 

Answer 5

 >>> s="17GB" >>> ind=map(str.isalpha,s).index(True) >>> num,suffix=s[:ind],s[ind:] >>> print num+":"+suffix 17:GB 

Answer 6

You should use regular expressions, grouping what you want to know:

 import re s = "17GB" match = re.match(r"^([1-9][0-9]*)\s*(GB|MB|KB|B)$", s) if match: print "Number: %d, unit: %s" % (int(match.group(1)), match.group(2)) 

Change the regular expression according to what you want to parse. If you are not familiar with regular expressions, this is a great site for tutorials.

Answer 7

How about using regex

http://python.org/doc/1.6/lib/module-regsub.html

Answer 8

For this task, I definitely use a regex:

 import re there = re.compile(r'\s*(\d+)\s*(\S+)') thematch = there.match(s) if thematch: number, unit = thematch.groups() else: raise ValueError('String %r not in the expected format' % s) 

In the RE pattern, \s means spaces, \d means number, \s means non-spaces; * means "0 or more of the preceding", + means "1 or more of the preceding", and parentheses enclose "capture groups", which are then returned by calling groups() on the match object. thematch - None if the given string does not match the pattern: optional spaces, then one or more numbers, then optional spaces, then one or more non-white characters).

Answer 9

Regular expression.

 import re m = re.match(r'\s*(?P<n>[-+]?[.0-9])\s*(?P<u>.*)', s) if m is None: raise ValueError("not a number with units") number = m.group("n") unit = m.group("u") 

This will give you a number (integer or fixed point), too complex to remove the scientific notation “e” from the device prefix) with an optional sign followed by units, with an optional space.

You can use re.compile() if you are going to make many matches.

Answer 10

This uses an approach that should be a little more forgiving than regular expressions. Note: this is not as effective as other solutions.

 def split_units(value): """ >>> split_units("2GB") (2.0, 'GB') >>> split_units("17 ft") (17.0, 'ft') >>> split_units(" 3.4e-27 frobnitzem ") (3.4e-27, 'frobnitzem') >>> split_units("9001") (9001.0, '') >>> split_units("spam sandwhiches") (0, 'spam sandwhiches') >>> split_units("") (0, '') """ units = "" number = 0 while value: try: number = float(value) break except ValueError: units = value[-1:] + units value = value[:-1] return number, units.strip() 

Answer 11

SCIENTIFIC NOTATION This regular expression works well for me to parse numbers that might be in scientific notation, and is based on recent python documentation about scanf: https://docs.python.org/3/library/re.html#simulating -scanf

 units_pattern = re.compile("([-+]?(\d+(\.\d*)?|\.\d+)([eE][-+]?\d+)?|\s*[a-zA-Z]+\s*$)") number_with_units = list(match.group(0) for match in units_pattern.finditer("+2.0e-1 mm")) print(number_with_units) >>>['+2.0e-1', ' mm'] n, u = number_with_units print(float(n), u.strip()) >>>0.2 mm 

Answer 12

try the regex pattern below. the first group (scanf () markers for any number anyway) is removed directly from the python documents for the re module.

 import re SCANF_MEASUREMENT = re.compile( r'''( # group match like scanf() token %e, %E, %f, %g [-+]? # +/- or nothing for positive (\d+(\.\d*)?|\.\d+) # match numbers: 1, 1., 1.1, .1 ([eE][-+]?\d+)? # scientific notation: e(+/-)2 (*10^2) ) (\s*) # separator: white space or nothing ( # unit of measure: like GB. also works for no units \S*)''', re.VERBOSE) ''' :var SCANF_MEASUREMENT: regular expression object that will match a measurement **measurement** is the value of a quantity of something. most complicated example:: -666.6e-100 units ''' def parse_measurement(value_sep_units): measurement = re.match(SCANF_MEASUREMENT, value_sep_units) try: value = float(measurement[0]) except ValueError: print 'doesn't start with a number', value_sep_units units = measurement[5] return value, units