# How to calculate CRC32 with Python to match online results?

Hello Guys, How are you all? Hope You all Are Fine. Today We Are Going To learn about How to calculate CRC32 with Python to match online results in Python. So Here I am Explain to you all the possible Methods here.

## How to calculate CRC32 with Python to match online results?

1. How to calculate CRC32 with Python to match online results?

Python 2 (unlike py3) is doing a signed 32-bit CRC.
Those sites are doing an unsigned 32-bit CRC.
The values are the same otherwise, as you can see from this:
`>>> 0x100000000 - 0xb1d4025b == 0x4e2bfda5 True`

2. calculate CRC32 with Python to match online results

Python 2 (unlike py3) is doing a signed 32-bit CRC.
Those sites are doing an unsigned 32-bit CRC.
The values are the same otherwise, as you can see from this:
`>>> 0x100000000 - 0xb1d4025b == 0x4e2bfda5 True`

## Method 1

Python 2 (unlike py3) is doing a signed 32-bit CRC.

Those sites are doing an unsigned 32-bit CRC.

The values are the same otherwise, as you can see from this:

```>>> 0x100000000 - 0xb1d4025b == 0x4e2bfda5
True
```

One quick way to convert from 32-bit signed to 32-bit unsigned is:*

```>>> -1311505829 % (1<<32)
2983461467
```

Or, in hex:

```>>> hex(-1311505829 % (1<<32))
'0xb1d4025b'
```

`& 0xFFFFFFFF` or `% 0x100000000` or `& (2**32-1)` or `% (2**32)` and so on are all equivalent ways to do the same bit-twiddling; it just comes down to which one you find most readable.

## Method 2

zlib.crc32 documentation suggests using the following approach “to generate the same numeric value across all Python versions and platforms”.

```import zlib
hex(zlib.crc32(b'hello-world') & 0xffffffff)
```

The result is `0xb1d4025b` as expected.

## Conclusion

It’s all About this issue. Hope all Methods helped you a lot. Comment below Your thoughts and your queries. Also, Comment below which Method worked for you? Thank You.