Can we change the linear expression's lines randomly in gurobi ??

Answered

Jacob Jin

August 29, 2022 07:57

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lin_exp_2 = K * sum(
    z_dual[i, l].x * model.getVarByName('z_' + str(i) + '_' + str(l)) for l in L for i in range(N + 1))
+ K * sum(r_dual[i, j].x * model.getVarByName('r_' + str(i) + '_' + str(j)) for j in range(N+1) for i in range(N+1))

If I use the expression above, the expression will not include the last line. 

lin_exp_2 = K * sum(
    z_dual[i, l].x * model.getVarByName('z_' + str(i) + '_' + str(l)) for l in L for i in range(N + 1)) + K * sum(r_dual[i, j].x * model.getVarByName('r_' + str(i) + '_' + str(j)) for j in range(N+1) for i in range(N+1))

The expression above is correct.

Why would that happen?

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• Official comment

  

  Simranjit Kaur

  • Gurobi Staff

  November 16, 2025 23:29

  This post is more than three years old. Some information may not be up to date. For current information, please check the Gurobi Documentation or Knowledge Base. If you need more help, please create a new post in the community forum, or try Gurobot, our chatbot interface offering instant, expert-level support.
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  Jaromił Najman

  • Gurobi Staff

  August 29, 2022 08:32 Edited

  It is quite hard to help here, because the snippets you provided are not reproducible.

  I would guess that it some identation + editor issue which is not correctly displayed. You should try using a backslash when you want to write multi line expressions in Python.

  lin_exp_2 = K * sum(
      z_dual[i, l].x * model.getVarByName('z_' + str(i) + '_' + str(l)) for l in L for i in range(N + 1)) \
  + K * sum(r_dual[i, j].x * model.getVarByName('r_' + str(i) + '_' + str(j)) for j in range(N+1) for i in range(N+1))

  If this does not help, you can always use parentheses to make sure that the whole expression is used instead of putting it into 1 long line.

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