|   | 1 |  initial version  | 
You can work in a polynomial ring.
sage: R.<a,b,c> = PolynomialRing(QQ)
sage: p = b * a + c * a + 3 * a + b + c
sage: p.coefficient(a*b)
1
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                Copyright Sage, 2010. Some rights reserved under creative commons license. Content on this site is licensed under a Creative Commons Attribution Share Alike 3.0 license.