PyCrypto Error: [Solved] Python3.9 Installation Immediately

PyCrypto Error: [Solved] Python3.9 Installation Immediately

Author: Amresh Mishra | Published On: May 12, 2024

Ah, the life of a programmer! One moment you’re on top of the world, deploying features like a boss, and the next, you’re banging your head against the keyboard because of an installation error. If you’ve found yourself here, you’re probably dealing with the infamous PyCrypto installation issue in Python 3.9. Fear not! This guide will help you troubleshoot and resolve this error without causing any more damage to your poor keyboard.

What is PyCrypto?

Before diving into the problem, let’s get to know our culprit a bit better. PyCrypto is a collection of secure hash functions and various encryption algorithms. It’s an essential library for anyone dealing with cryptographic operations in Python. Whether you’re encrypting data, working with secure communications, or just need some hashing functions, PyCrypto has been a go-to library.

pycrypto Error: [Solved] Python3.9 Installation Immediately

The Problem with Python 3.9

Here’s the kicker: PyCrypto hasn’t been maintained for quite some time, and Python 3.9 introduced some changes that broke compatibility with PyCrypto. So, if you’re using Python 3.9 and trying to install PyCrypto, you’re likely to encounter a big, fat error message. Frustrating, right?

The Dreaded Error Message

When attempting to install PyCrypto using pip, you might run into an error message that looks something like this:

Collecting pycrypto
  Using cached pycrypto-2.6.1.tar.gz (446 kB)
    ERROR: Command errored out with exit status 1:
     command: /usr/bin/python3.9 -c 'import sys, setuptools, tokenize; sys.argv[0] = '"'"'/tmp/pip-install-4i_yj8tt/pycrypto/'"'"'; __file__='"'"'/tmp/pip-install-4i_yj8tt/pycrypto/'"'"';f=getattr(tokenize, '"'"'open'"'"', open)(__file__);'"'"'\r\n'"'"', '"'"'\n'"'"');f.close();exec(compile(code, __file__, '"'"'exec'"'"'))' egg_info --egg-base /tmp/pip-pip-egg-info-pymvhxn_
         cwd: /tmp/pip-install-4i_yj8tt/pycrypto/
    Complete output (15 lines):
    Traceback (most recent call last):
      File "<string>", line 1, in <module>
      File "/tmp/pip-install-4i_yj8tt/pycrypto/", line 456
        print text
    SyntaxError: Missing parentheses in call to 'print'. Did you mean print(text)?

## Why is This Happening?

The short version: PyCrypto’s code is outdated. The error above occurs because PyCrypto’s `` script contains syntax that is incompatible with Python 3.9. Specifically, it’s using the old `print` statement instead of the function `print()`. Python 3.9 does not support this syntax, leading to the installation failure.

## **The Solution(s)**

### Option 1: Use PyCryptodome Instead

PyCryptodome is a drop-in replacement for PyCrypto. It’s actively maintained and compatible with newer versions of Python. The easiest and most recommended solution is to switch to PyCryptodome. Here’s how you can do it:

1. **Uninstall PyCrypto** (if you have it installed):

pip uninstall pycrypto

2. **Install PyCryptodome**:

pip install pycryptodome

3. **Update Your Imports**:
   In your Python code, replace `Crypto` with `Cryptodome`. For example:

from Crypto.Cipher import AES


from Cryptodome.Cipher import AES

### Option 2: Use an Older Version of Python

If, for some reason, you must use PyCrypto and cannot switch to PyCryptodome, you might consider downgrading your Python version. PyCrypto works well with Python 3.8 and earlier versions. Here’s how to do it:

1. **Uninstall Python 3.9**:
   The method to uninstall Python 3.9 will depend on your operating system.

2. **Install Python 3.8**:
   - On **Windows**, download the installer from [](
   - On **macOS** or **Linux**, use a package manager. For example, on Ubuntu:
     sudo apt-get install python3.8

3. **Create a Virtual Environment**:
   Create a virtual environment with Python 3.8:

python3.8 -m venv myenv
source myenv/bin/activate

4. **Install PyCrypto**:

pip install pycrypto

### Option 3: Modify PyCrypto Source Code

If you’re feeling adventurous and have some knowledge of Python, you can try modifying the PyCrypto source code to make it compatible with Python 3.9. This method is not recommended unless you really know what you’re doing, as it can lead to further issues down the line.

1. **Download PyCrypto Source Code**:

tar -xzvf pycrypto-2.6.1.tar.gz
cd pycrypto-2.6.1

2. **Edit ``**:
   Open the `` file in a text editor and replace all instances of `print` statements with `print()` function calls.

3. **Build and Install**:

python3.9 build
python3.9 install

## A Step-by-Step Guide to Switching to PyCryptodome

Let’s dive deeper into Option 1, which is the recommended approach.

### Step 1: Uninstall PyCrypto

First, make sure PyCrypto is uninstalled. Open your terminal or command prompt and type the following command:

pip uninstall pycrypto

### Step 2: Install PyCryptodome

Next, install PyCryptodome, which is fully compatible with Python 3.9 and actively maintained. Run the following command:

pip install pycryptodome

### Step 3: Update Your Imports

Now, you need to update your Python code to use PyCryptodome instead of PyCrypto. This mainly involves changing your import statements. Here’s an example:


from Crypto.Cipher import AES
from Crypto.PublicKey import RSA
from Crypto.Random import get_random_bytes


from Cryptodome.Cipher import AES
from Cryptodome.PublicKey import RSA
from Cryptodome.Random import get_random_bytes

### Step 4: Test Your Code

Finally, run your Python scripts to ensure everything is working correctly. If you encounter any issues, double-check your import statements and ensure all instances of `Crypto` are replaced with `Cryptodome`.

## Common Errors and How to Fix Them

Even after switching to PyCryptodome, you might encounter some issues. Here are a few common problems and their solutions:

### ImportError: No module named 'Cryptodome'

This error occurs if PyCryptodome is not installed correctly. Make sure you’ve installed it using `pip`:

pip install pycryptodome

### AttributeError: module 'Cryptodome.Cipher' has no attribute 'AES'

Ensure that your import statements are correct. The correct way to import AES from PyCryptodome is:

from Cryptodome.Cipher import AES

Also Read:

ValueError: Incorrect AES key length

If you get this error, it means the key length you’re using is not valid for AES. AES supports key lengths of 16, 24, or 32 bytes. Double-check your key length and ensure it’s one of these values.

A Little Humor to Brighten Your Day

Programming can be a daunting task, especially when you’re dealing with annoying errors. Here are a few jokes to lighten the mood:

  • Why do programmers prefer dark mode? Because the light attracts bugs!
  • How many programmers does it take to change a light bulb? None, that’s a hardware problem.
  • Why do Python programmers wear glasses? Because they can’t C.


Q: Why is PyCrypto not maintained anymore?

A: The original maintainer of PyCrypto stopped maintaining the library several years ago. As a result, it’s no longer updated to support new versions of Python. PyCryptodome was created as a fork to continue the development and provide compatibility with newer Python versions.

Q: What are the main differences between PyCrypto and PyCryptodome?

A: PyCryptodome is a drop-in replacement for PyCrypto with additional features and improvements. It’s actively maintained, supports newer Python versions, and includes new cryptographic algorithms that PyCrypto doesn’t have.

Q: How do I uninstall Python 3.9 and install an older version on Windows?

A: To uninstall Python 3.9, go to the Control Panel, select “Programs and Features,” find Python 3.9, and click “Uninstall.” To install an older version, download the installer from and follow the installation instructions.


Dealing with the PyCrypto installation error in Python 3.9 can be a real headache, but with the right approach, you can overcome this obstacle. Whether you choose to switch to PyCryptodome, downgrade your Python version, or modify the PyCrypto source code, each method has its own pros and cons.

For most users, switching to PyCryptodome is the easiest and most effective solution. It ensures you’re using a library that’s actively maintained and compatible with the latest versions of Python. Plus, it requires minimal changes to your existing code.

Remember, programming is a journey filled with challenges and learning opportunities. Every error encountered and resolved makes you a better programmer. So, keep your chin up, stay curious, and don’t forget to enjoy the process. Happy coding!

Author: Amresh Mishra
Amresh Mishra is a passionate coder and technology enthusiast dedicated to exploring the vast world of programming. With a keen interest in web development, software engineering, and emerging technologies, Amresh is on a mission to share his knowledge and experience with fellow enthusiasts through his website,

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