Parti ouvrier français
Pastre was born in Gallargues-le-Montueux. At first he joined the French Workers' Party (POF), which in 1902 merged into the Socialist Party of France (PSdF), which in turn merged into the French Section of the Workers' International (SFIO) in 1905. Pastre was a member of the Chamber of Deputies from 1898 to 1910.