Bourbaki

Corollary 3

Tag 020Z, permanent. Cite it as [Bourbaki, Tag 020Z].

Topologie algébrique, chapter IV, § 2. Groupes de Poincaré des espaces délaçables

Let X and Y be topological spaces and let f:X→Yf: X\rightarrow Y be a continuous and relatively connected mapping. Let F be a set and let g:X→Fg: X\rightarrow F be a locally constant mapping. There exists a unique locally constant mapping h:Y→Fh: Y\rightarrow F such that g=h∘fg=h\circ f.

The restriction of gg to every connected component of X is constant. By Corollary 1, there exists a mapping h:Y→Fh: Y\rightarrow F, constant on each connected component of Y, such that g=h∘fg=h\circ f. The mapping hh is locally constant, since the connected components of Y are open. The uniqueness of such a mapping follows from the fact that f(X)f(X) is dense in Y.

Bourbaki sets the proof directly after the statement, and the corpus does not separate them, so what is above is the statement and its proof together.

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Machine translation of the English, by gpt-5.4, against glossary version 34. Not checked by a person.