Part of the generation of Hungarian poets who grew up after the 1956 Uprising, Petri employs a black humor almost medieval in feeling for his savage attacks on the political system of the Warsaw Pact countries.
He was born in 1943 to a multi-ethnic Jewish family in Budapest. After his father's death he was raised by his mother, grandparents and aunts. According to his remembrance, he turned to poetry at 11 or 12, and from the early 1960s he published in such renowned periodicals as Kortárs and Élet és Irodalom. Disillusioned by their style himself, he never let any of those writings be re-issued, and soon he developed intention to change career. During the following years he nursed at a mental clinic as a preliminary exercise for planned psychiatry studies, resigning from which he showed interest in economics and law, but later he decided to be a philosopher. He informally attended philosophy classes at Eötvös Loránd University, Budapest. In 1966 he finally enrolled at Eötvös Loránd University with a Philosophy and Literature major, without ever graduating. His most inspiring professors were György Márkus, Endre Simon and György Lukács.