Find all the numbers in a string using regular expression in Python

Extracting numbers from text is a common requirement in Python data analytics. Regular expressions provide a powerful way to define patterns for matching digits, decimal numbers, and numbers with signs.

Basic Number Extraction

The re.findall() function extracts all occurrences of a pattern from a string. The pattern r'\d+' matches one or more consecutive digits ?

import re

text = "Go to 13.8 miles and then -4.112 miles."
numbers = re.findall(r'\d+', text)
print(numbers)

['13', '8', '4', '112']

Note that this pattern extracts only digits, splitting decimal numbers and ignoring signs.

Extracting Complete Numbers with Decimals

To capture complete decimal numbers including signs, we need a more comprehensive pattern ?

import re

text = "Go to 13.8 miles and then -4.112 miles."
numbers = re.findall(r'[-+]?\d*\.?\d+', text)
print(numbers)

['13.8', '-4.112']

Pattern Breakdown

Let's understand the pattern r'[-+]?\d*\.?\d+' ?

import re

# Pattern components:
# [-+]?    - Optional plus or minus sign
# \d*      - Zero or more digits before decimal
# \.?      - Optional decimal point
# \d+      - One or more digits after decimal

text = "Price: $25.99, Temperature: -10.5°C, Quantity: +100"
numbers = re.findall(r'[-+]?\d*\.?\d+', text)
print("Numbers found:", numbers)

# Alternative pattern for integers only
integers = re.findall(r'[-+]?\d+', text)
print("Integers only:", integers)

Numbers found: ['25.99', '-10.5', '+100']
Integers only: ['25', '99', '-10', '5', '+100']

Different Number Formats

Here are patterns for various number formats ?

import re

text = "Scientific: 1.5e-4, Percentage: 95%, Currency: $1,234.56"

# Scientific notation
scientific = re.findall(r'[-+]?\d*\.?\d+[eE][-+]?\d+', text)
print("Scientific:", scientific)

# Percentages
percentages = re.findall(r'\d+\.?\d*%', text)
print("Percentages:", percentages)

# Currency (with commas)
currency = re.findall(r'\$\d{1,3}(?:,\d{3})*\.?\d*', text)
print("Currency:", currency)

Scientific: ['1.5e-4']
Percentages: ['95%']
Currency: ['$1,234.56']

Comparison of Patterns

Conclusion

Use r'\d+' for simple digit extraction, r'[-+]?\d*\.?\d+' for complete decimal numbers with signs. Adjust the pattern based on your specific number format requirements.