How do i find the 3 digit number in a string python?

I have a long text line with a lot of random words and numbers, i wish to assign a variable to the only 3 digit number in the line.

The number changes every different line but it is always only 3 digits. How does one search for the only 3 digit number in a linepython? There may be some 3 letter words so it must just be the number.

09824747 18 n 02 archer 0 bowman 0 003 @ 09640897 n 0000

in this example i want the variable digits = 003

asked Jun 12, 2013 at 13:54

JohnConneelyJohnConneely

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A regular expression with \b word boundaries would do the trick:

re.findall(r'\b\d{3}\b', inputtext)

returns a list of all 3-digit numbers.

Demo:

>>> import re
>>> inputtext = '09824747 18 n 02 archer 0 bowman 0 003 @ 09640897 n 0000'
>>> re.findall(r'\b\d{3}\b', inputtext)
['003']
>>> inputtext = 'exact: 444, short: 12, long: 1234, at the end of the line: 456'
>>> re.findall(r'\b\d{3}\b', inputtext)
['444', '456']

answered Jun 12, 2013 at 13:58

Martijn Pieters♦Martijn Pieters

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You can use regular expressions. Or look for a digit, then check the next two characters manually.

I would use a regexp:

import re

threedig = re.compile(r'\b(\d{3})\b') # Regular expression matching three digits.

The \b means "word boundary", and (\d{3}) means "three digits", the parenthesis makes it a "group" so the matching text can be found.

Then search using:

mo = threedig.search("09824747 18 n 02 archer 0 bowman 0 003 @ 09640897 n 0000")
if mo:
  print mo.group(1)

The above prints 333.

answered Jun 12, 2013 at 13:56

2

A solution thanks to regular expressions:

>>> s = "007 09824747 18 n 02 archer 0 bowman 0 003 @ 09640897 n 0000 008"
>>> r = re.findall(r'(?:[^\d]|\A)(\d{3})(?:[^\d]|\Z)', s)
>>> r
['007', '003', '008']

answered Jun 12, 2013 at 14:01

EmmanuelEmmanuel

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In Python, I got the following to work (based on the answers above):

re.compile('prefix\d{1,3}\suffix')})

This covers the scenario for anywhere between 1-3 digits

answered Apr 30, 2018 at 17:15

raTMraTM

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Format a number to 3 digits in Python #

Use a formatted string literal to format a number to 3 digits, e.g. result = f'{my_int:03d}'. The formatted string literal will format the number to the specified fixed length by adding leading zeros.

Copied!
from random import randint

my_int = 5

# ✅ pad number with leading zeros (formatted-string literal)

result = f'{my_int:03d}'
print(result)  # 👉️ '005'

# -----------------------------------

# ✅ pad number with leading zeros (zfill)

result = str(my_int).zfill(3)
print(result)  # 👉️ '005'

# ----------------------------------

# ✅ get first 3 digits of number
result = str(1234567)[:3]
print(result)  # 👉️ 123

# ----------------------------------

# ✅ generate random 3 digit number

result = randint(100, 999)
print(result)  # 👉️ 465

# ----------------------------------

# ✅ generate list of 3 digit numbers

my_list = [f'{item:03d}' for item in range(10)]

# 👇️ ['000', '001', '002', '003', '004', '005', '006', '007', '008', '009']
print(my_list)

The first example uses a formatted string literal to format a number to 3 digits by adding leading zeros.

Copied!
my_int = 5


result = f'{my_int:03d}'
print(result)  # 👉️ '005'

print(f'{9:03d}') # 👉️ 009

Formatted string literals (f-strings) let us include expressions inside of a string by prefixing the string with f.

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my_str = 'The number is:'
my_int = 137

result = f'{my_str} {my_int}'
print(result)  # 👉️ The number is: 137

Make sure to wrap expressions in curly braces - {expression}.

Formatted string literals also enable us to use the format specification mini-language in expression blocks.

Alternatively, you can use the str.zfill() method.

Format a number to 3 digits using str.zfill() #

To format a number to 3 digits:

1. Use the str() class to convert the number to a string.
2. Use the str.zfill() method to format the number to 3 digits.
3. The str.zfill() method will format the number to 3 digits by left-filling it with 0 digits.

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my_int = 5


result = str(my_int).zfill(3)
print(result)  # 👉️ '005'

The str.zfill method takes the width of the string and left-fills the string with 0 digits to make it of the specified width.

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num = 13


result_1 = str(num).zfill(3)
print(result_1)  # 👉️ '013'

result_2 = str(num).zfill(4)
print(result_2)  # 👉️ '0013'

Converting the number 13 to a string gives us a string with a length of 2.

Passing 3 as the width to the zfill() method means that the string will get left-filled with a single 0 digit.

If you need to get the first 3 digits of an integer, convert the integer to a string and use string slicing.

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result = str(1234567)[:3]
print(result)  # 👉️ '123'

my_int = int(result)
print(my_int)  # 👉️ 123

The slice goes from index 0 up to, but not including the digit at index 3.

If you need to generate a random 3-digit number, use the randint() function.

Copied!
from random import randint


result = randint(100, 999)
print(result)  # 👉️ 465

The random.randint function takes 2 numbers - a and b as parameters and returns a random integer in the range.

Note that the range is inclusive - meaning both a and b can be returned.

If you need to generate a list of 3-digit numbers, use a list comprehension.

Copied!
my_list = [f'{item:03d}' for item in range(10)]

# 👇️ ['000', '001', '002', '003', '004', '005', '006', '007', '008', '009']
print(my_list)

We used a list comprehension to iterate over a range of numbers.

List comprehensions are used to perform some operation for every element or select a subset of elements that meet a condition.

On each iteration, we use a formatted string literal to pad the current number with leading zeros to a length of 3.

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