What is Numbers Regex?

In Go (Golang), numbers can be validated using regular expressions via the built-in regexp package. These expressions help check patterns like integers or digit-only fields.

Go regex is often used for:

• Validating form fields like age, IDs, and quantities

• Extracting or matching numerical sequences in text

• Cleaning data by filtering out invalid numeric entries

Regex Pattern for Integer Decimal Numbers

To match integer decimal numbers that may include an optional leading plus (+) or minus (-) sign, you can use the following regular expression:

[+-]?\b[0-9]

How it works:

• [+-]? — Matches an optional plus or minus at the start.

• \b — Word boundary ensures we match whole numbers and not numbers embedded within words.

• [0-9]+ — Matches one or more digits.

This pattern is supported in popular flavors including .NET, Java, JavaScript, PCRE, Perl, Python, and Ruby. Use it in your codebase, test forms, or simulations where numeric input formats need validation.

Regex for Signed Integers

To match a string that contains only an integer (with an optional plus or minus sign), use the following regex pattern:

^[+-]?[0-9]

• ^ asserts the start of the string.

• [+-]? allows for an optional "+" or "-" sign.

• [0-9]+ matches one or more digits.

• $ ensures it matches the entire string, not just a part of it.

This pattern will validate numbers like "42", "-17", or "+100", but reject any strings containing letters, spaces, or decimals. Use it to ensure your input truly represents a signed integer.

Checking for Positive Integer Strings

To verify that a string consists exclusively of a positive integer in decimal notation (no negative sign, no decimals), use the following regular expression pattern:

^[0-9]

This pattern ensures the string:

• Begins (^) and ends ($) with one or more digits ([0-9]+)

• Contains only digits, with no extra characters or spaces

This regex works in most flavors, including Python, Java, JavaScript, Go, Perl, and Ruby. No special options are required.

Common Regex Patterns for Numbers:

• ^\d+$ : Matches a positive integer (e.g., 12345)

• ^\d+\.\d+$ : Matches a decimal number (e.g., 3.14, 0.75)

• ^\d{1,3}(,\d{3})*$ : Matches formatted numbers with commas (e.g., 1,000 or 100,000)

• ^-?\d+$ : Matches integers with optional minus sign (e.g., -42)

• ^-?\d+\.\d+$ : Matches signed decimal numbers (e.g., -3.14)

Examples with Go Code

Example 1: Validate Integer Numbers

Try it in the Go Regex Tester

package main

import (
    "fmt"
    "regexp"
)

func main() {
    pattern := regexp.MustCompile(`^\d+$`)
    input := "45678"
    isValid := pattern.MatchString(input)
    fmt.Printf("Is '%s' a valid integer? %t\n", input, isValid)
}

Example 2: Match Decimal Numbers

Use this along with Phone Number Generator to simulate full input forms.

package main

import (
    "fmt"
    "regexp"
)

func main() {
    pattern := regexp.MustCompile(`^\d+\.\d+$`)
    input := "123.45"
    isValid := pattern.MatchString(input)
    fmt.Printf("Is '%s' a valid decimal? %t\n", input, isValid)
}

Example 3: Match Formatted Prices

Combine with Zipcode Generator for e-commerce data validation.

package main

import (
    "fmt"
    "regexp"
)

func main() {
    pattern := regexp.MustCompile(`^\d{1,3}(,\d{3})*$`)
    input := "12,345"
    isValid := pattern.MatchString(input)
    fmt.Printf("Is '%s' a valid formatted number? %t\n", input, isValid)
}

Finding Positive Integer Decimal Numbers with Regex

Need to pick out standalone positive integers from a chunk of text? Regular expressions have you covered, and there are a few reliable patterns you can use depending on your target language.

Basic Pattern: Match Standalone Numbers

A great starting point is this simple pattern:

\b[0-9]

• \b matches a word boundary, ensuring you capture only whole numbers and not parts of larger words or numbers.

• [0-9]+ matches one or more digits.

This pattern works smoothly in most major regex engines—think .NET, JavaScript, Python, Java, PCRE, Perl, and Ruby.

Adapting for Different Languages

Some languages have quirks when it comes to lookbehind support. For instance:

• Languages like .NET and Java can handle lookbehinds, so you could use something like:

  (?<=^\s)[0-9]

  This matches numbers at the start of a line or after whitespace, and ensures the match ends before whitespace or the end of the line.

• For Python and Perl, since lookbehinds need fixed-width patterns, adjust to:

  (?:^(?<=\s))[0-9]

  Here, the non-capturing group handles line starts or whitespace more flexibly.

Capturing Numbers with Leading Spaces

If you want to include any leading whitespace in your match, just tweak your regex:

(^\s)([0-9]

Now, your first group captures any starting space (or start of line), and the second group grabs the entire integer.

Across all these options, you'll find support in regex flavors like .NET, Java, JavaScript, PCRE, Perl, Python, and Ruby. Remember to test your pattern in the https://qodex.ai/all-tools/go-regex-tester or your favorite validator to confirm it matches your data and language.

Matching Numbers with Leading Whitespace

Need your regex to find numbers even when there’s a space (or several) before them? Here’s a straightforward way to adjust your pattern. By including (^\s) at the start of your regex, you instruct it to match numbers that either appear at the beginning of a line or are preceded by whitespace. For example:

(^\s)([0-9]

• (^\s): Matches the start of the string or any whitespace before the number

• ([0-9]+): Matches one or more digits

• (?=$\s): Ensures the number is followed by either whitespace or the end of the string

This approach works across multiple regex flavors including JavaScript, Python, Java, .NET, Ruby, and PCRE. Perfect for extracting standalone positive integers wherever they might hide in your text, even if users get a bit generous with the space bar.

Matching Standalone Positive Integers in Text

To match positive integers that aren't attached to other words or symbols in a larger block of text, you can use a regular expression pattern that ensures they're surrounded by word boundaries or spaces.

For most regex engines like .NET, Java, PCRE, or Ruby 1.9, a common approach is to use lookbehind and lookahead assertions. For example:

(?<=^\s)[0-9]

• (?<=^\s) ensures the number is either at the start of a line or follows whitespace.

• [0-9]+ matches one or more digits (your positive integer).

• (?=$\s) ensures the number is at the end of a line or followed by whitespace.

Note on Perl and Python

Not all languages support the exact same lookbehind approach. For Perl and Python, you need to adjust the pattern since their engines require lookbehinds of fixed length. Here, you’d typically use a non-capturing group instead:

(?:^(?<=\s))[0-9]

• (?:^(?<=\s)) starts your match at the beginning of text or after a space.

• The rest of the pattern remains as above to ensure proper boundaries.

When testing across multiple languages like Python, Perl, or Ruby, always double-check regex flavor compatibility for best results.

Regex Patterns for Detecting Integers Across Languages

Need to validate integer numbers in your favorite language? Here’s how you can spot positive and signed integers, with regex flavors that suit .NET, Java, JavaScript, PCRE, Perl, Python, and Ruby.

Match positive integers in a larger text

To find standalone positive integers (like “42” in “We found 42 apples”), try:

\b[0-9]

Compatible with:

• .NET, Java, JavaScript, PCRE, Perl, Python, Ruby

Check if a string contains only a positive integer

For confirming whether your text is just a positive integer (and nothing else), use:

^[0-9]

Compatible with:

• .NET, Java, JavaScript, PCRE, Perl, Python

Spot integers with optional leading sign

Want to account for +12 or -8? This pattern does just that:

[+-]?\b[0-9]

Compatible with:

• .NET, Java, JavaScript, PCRE, Perl, Python, Ruby

Verify if a string is just a signed or unsigned integer

For precise validation (the entire input is an integer, optionally signed):

^[+-]?[0-9]

Compatible with:

• .NET, Java, JavaScript, PCRE, Perl, Python, Ruby

When working across multiple platforms, these patterns cover most developer needs, whether you’re extracting numbers from logs, validating user input, or generating test cases. No matter if you’re elbow-deep in Python scripts or fine-tuning your Java backend, these regexes keep your numeric extractions tidy and accurate.

Regex Lookbehind: Compatibility Quirks Across Languages

When using lookbehind assertions in regex to hunt for integers, you’ll quickly discover not all languages play by the same rules. Some, like .NET, Java, and recent versions of JavaScript and Ruby, handle lookbehinds with flair—even letting you match patterns where what's behind the number varies in length. Others, like Perl and Python, are more rigid: their lookbehinds require a fixed-width pattern.

This matters if you, for example, want to capture standalone numbers surrounded by spaces or at the start and end of text. In Go, .NET, and Java, you might use a variable-length lookbehind to elegantly spot these numbers. But in Python or Perl, you’ll have to rewrite your regex logic, perhaps by using non-capturing groups or adjusting your approach to avoid tripping over their stricter syntax rules.

In summary: Regex flavor influences how you craft patterns for numerical searches. Double-check the syntax and feature set for your chosen language to ensure your validator works smoothly, especially with tricky lookbehind scenarios.

Pro Tips

• Use MustCompile in Go for reusable regex patterns.

• For optional decimals, use ^\d+(\.\d+)?$

• Always anchor your pattern with ^ and $ for full match.

• Avoid overly permissive patterns—test edge cases like 0001, -0.0, etc.

  
  

How It Works

1. Paste your number regex pattern or use a preset.

2. Enter the test number input in the field.

3. Instantly see if it matches.

4. Adjust and refine your pattern live.

Use Cases

• Form validation for user IDs, age, or price fields

• Data cleaning for CSV imports with numeric columns

• Enterprise software input handling (billing, invoices, etc.)

• QA test scenarios for edge-case inputs

• Simulated e-commerce order totals

  
  

Combine With These Tools

• Go Regex Tester: Test full regex patterns in Go with live feedback.

• Email Generator: Create realistic emails for form validations.

• Phone Number Generator: Pair with numeric validation for sign-up fields.

• Password Generator: Validate numeric or alphanumeric password rules.

• Username Generator: Generate full test profiles.