How to reproduce PHP's bindec() function in Python

M66 2025-05-29

In PHP, the bindec() function is used to convert binary strings into decimal numbers and is a very practical tool when processing binary data. For example:

 <?php
echo bindec("1101"); // Output 13
?>

There is no built-in function in Python with the same name as bindec() , but we can implement the same function very simply. This article will use several examples to explain in detail how to simulate PHP's bindec() function in Python.

1. Basic implementation method

Python's built-in function int() can convert arbitrary strings into decimal, just need to provide the correct cardinality. For example:

 binary_string = "1101"
decimal_number = int(binary_string, 2)
print(decimal_number)  # Output 13

This int(binary_string, 2) achieves the same effect as bindec("1101") .

2. Encapsulated as a function

To be closer to how PHP is used, we can encapsulate a function called bindec :

 def bindec(binary_string):
    try:
        return int(binary_string, 2)
    except ValueError:
        raise ValueError("The entered string is not a valid binary format")

How to use it is as follows:

 print(bindec("1010"))  # Output 10

3. Advanced implementation of handling symbol bits

In PHP, bindec() treats the binary string as a complement form and converts it into a signed decimal number. For example:

 echo bindec("11111111111111111111111111111111"); // Output -1

In this case, bindec() treats all 32-bit 1s as -1 (a signed integer). To achieve similar effects in Python, we need to manually judge the symbol bits:

 def bindec_signed(binary_string):
    length = len(binary_string)
    value = int(binary_string, 2)
    if binary_string[0] == '1':
        # Complement to sign
        value -= 1 << length
    return value

Example:

 print(bindec_signed("11111111111111111111111111111111"))  # Output -1
print(bindec_signed("10000000000000000000000000000000"))  # Output -2147483648

4. How to determine the validity of input

To prevent illegal strings from entering, we can first verify that the string is in pure binary format:

 def is_valid_binary(s):
    return all(c in '01' for c in s)

Use in combination:

 def bindec_safe(binary_string):
    if not is_valid_binary(binary_string):
        raise ValueError("Illegal binary string")
    return int(binary_string, 2)

5. Online testing tool recommendation

To facilitate you to test these codes on web pages, you can use an online Python execution environment, for example:

https://m66.net/tools/python/
https://m66.net/code/playground/

You just need to copy the above code to a web page to run to get the results, which is very convenient for debugging.

6. Summary

Although Python does not have a built-in bindec() function, through the int() function and simple logical processing, we can completely simulate this function in PHP, and even make it more powerful:

The basic functions can be realized by int(binary, 2) ;
If you want to simulate PHP's complement behavior, you can use bindec_signed() ;
Adding exception and validity handling can improve robustness.

I hope this tutorial can help you successfully migrate the relevant logic of bindec() in cross-language development.

bindec