Discrepancy between 3DES in OpenSSL and PyDES
In Python and on that website, you're entering a key. A 3-DES key consists of 24 bytes. You picked a key that's some nice printable text, but a key in general is binary, randomly generated.

With the OpenSSL command line, you're supplying a password (or passphrase, the two words are synonyms). A password is not a key: it's typically not fully random, consists only of printable characters, can have any length, ...

OpenSSL uses a key derivation mechanism to calculate a key from that password. To generate a key from a password, you need to perform stretching and randomize the process with a salt, which OpenSSL does, although not very well.

To get the same result with openssl en, tell it that you're supplying a key, with the -K option.

Generally speaking, the openssl command line is more of a demonstration tool than a tool for serious usage. This is especially true of commands like enc. Don't expect things to be secure unless you have a very precise of what you're doing.

In any case...


  triple DES ECB


Hopefully this is for learning purposes, and even then, neither 3DES nor ECB have any advantage for learning. 3DES is an obsolete algorithm with no benefit over the modern standard AES or modern alternatives such as Camellia and ChaCha20. ECB is not really a proper mode, it's “don't bother with a proper mode”, and it isn't secure (so why bother encrypting?). Use a mode such as CTR or CBC for encryption (and learn to use an IV, which is necessary for any mode), or a mode such as GCM or CCM for authenticated encryption.