What is "py"

n. (context computing English) an abbreviation for Python programming language

PY, Py, py or P-Y may stand for:

• Pack year, a quantification of cigarette smoking
• Peace by Youth, a local youth-led nonprofit organization from district Jacobabad, Sindh, Pakistan. Details at www.py.org.pk
• Pinyin, a system of romanization (phonetic notation and transliteration to Roman script) for Mandarin Chinese
• Py (cipher), a stream cipher designed by Eli Biham and Jennifer Seberry
• Paraguay, ISO 3166-1 country code
  • .py, the country code top level domain (ccTLD) for Paraguay
• The Python programming language's typical filename extension, '.py'
• The Portsmouth yardstick, used as a rating system in yacht racing and dinghy racing
• Delphine Py-Bilot, a French triathlete
• Eugène Py, a French cinema pioneer of the Cinema of Argentina
• Olivier Py, a French stage director, actor and writer
• Pierre-Yves Gerbeau, French businessman
• Py, Pyrénées-Orientales, a commune of the Pyrénées-Orientales département in southwestern France
• Surinam Airways IATA airline designator
• Pyridine, a common monodentate ligand in coordination chemistry, abbreviated as 'py'
• Permalloy, a nickel-iron magnetic alloy
• Piye, a Kushite king and founder of the Twenty-fifth dynasty of Egypt
• p-y method, for assessing the load-bearing abilities of deep foundations

Py is a stream cipher submitted to eSTREAM by Eli Biham and Jennifer Seberry. It is one of the fastest eSTREAM candidates at around 2.6 cycles per byte on some platforms. It has a structure a little like RC4, but adds an array of 260 32-bit words which are indexed using a permutation of bytes, and produces 64 bits in each round.

The authors assert that the name be pronounced "Roo", a reference to the cipher's Australian origin, by reading the letters "Py" as Cyrillic (Ру) rather than Latin characters. This somewhat perverse pronunciation is understood to be their answer, in jest, to the difficult-to-pronounce name Rijndael for the cipher which was adopted as the Advanced Encryption Standard.

• The original April 2005 proposal included the cipher Py, and a simplified version Py6. The latter reduces the size of some internal tables, providing greatly reduced key scheduling cost, at the expense of a shorter maximum output length.
• In June 2006, the authors described Pypy (even more confusingly, half-Cyrillic Pyру and thus pronounced "Pyroo") as an optional stronger variant. This omits one of the output words from each iteration of Py, and thus operates at slightly over half the speed of Py. (Actually about 0.6×.)
• In January 2007, the key schedule algorithm was changed, producing "tweaked" variants TPy, TPypy and TPy6. To be precise, the first (key-dependent) phase is unmodified, but the second (IV setup) phase has an error corrected. The round functions used to produce output are identical.
• At Indocrypt 2007, Gautham Sekar, Souradyuti Paul and Bart Preneel proposed two new ciphers RCR-32 and RCR-64 based on the design principles of Pypy and Py, respectively. These replace a variable rotate in Py with a fixed rotate, eliminating an attack and speeding up the cipher slightly. The TPy key schedule is used unmodified.