Pyat studied law but eventually quit the bar in order to pursue a career as a radical journalist. He carried on a literary war against Romanticism, condemning it as “reactionary,” and wrote a number of plays. During the 1848 revolution Pyat was a Montagnard (radical) deputy. His participation in the insurrection of June 1849 forced him to flee the country and remain in exile for 20 years. During this period Pyat was active in socialist groups in Switzerland, Belgium, and England.

Returning to France after the 1869 amnesty, Pyat wrote so many seditious articles that he had to flee a second time. The fall of the Second Empire enabled him to return to Paris; elected to the National Assembly in February 1871, he refused to vote for peace with Germany and was elected to the Commune, the leftist government of Paris, in March. After the fall of the Commune, Pyat fled France a third time. Though he was condemned to death in his absence, he was allowed to return after the amnesty of 1880. In 1888 he was elected deputy for Marseille and was active in the opposition to General Georges Boulanger, who threatened a coup d'état against the Third Republic.