how can i resolve "com.fasterxml.jackson.core.JsonParseException" problem?

Question

I faced this problem when I ran the code on Azure Synapse Analytics using Notebook.

I run this code

# Instantiate our problem class
model = pulp.LpProblem("Profit_maximising_problem", LpMaximize)

A = pulp.LpVariable('A', lowBound=0, cat='Integer')
B = pulp.LpVariable('B', lowBound=0, cat='Integer')

# Objective function
model += 30000 * A + 45000 * B, "Profit"

# Constraints
model += 3 * A + 4 * B <= 30
model += 5 * A + 6 * B <= 60
model += 1.5 * A + 3 * B <= 21

# Solve our problem
model.solve()
pulp.LpStatus[model.status]

# Print our decision variable values
print "Production of Car A = {}".format(A.varValue)
print "Production of Car B = {}".format(B.varValue)

# Print our objective function value
print pulp.value(model.objective)

I got this code from this link http://benalexkeen.com/linear-programming-with-python-and-pulp-part-3/.

So, I follow step by step but when I run model.solve() I will get the error like this.

1. com.fasterxml.jackson.core.JsonParseException: Unrecognized token 'Welcome': was expecting (JSON String, Number, Array, Object or token 'null', 'true' or 'false')
 at [Source: (String)"Welcome to the CBC MILP Solver "; line: 1, column: 8]

2. com.fasterxml.jackson.core.JsonParseException: Unrecognized token 'command': was expecting (JSON String, Number, Array, Object or token 'null', 'true' or 'false')
 at [Source: (String)"command line - /home/trusted-service-user/cluster-env/env/lib/python3.8/site-packages/pulp/apis/../solverdir/cbc/linux/64/cbc /tmp/29f229eb8406409583a8333341306957-pulp.mps max timeMode elapsed branch printingOptions all solution /tmp/29f229eb8406409583a8333341306957-pulp.sol (default strategy 1)"; line: 1, column: 8]

3. com.fasterxml.jackson.core.JsonParseException: Unrecognized token 'At': was expecting (JSON String, Number, Array, Object or token 'null', 'true' or 'false')
 at [Source: (String)"At line 3 ROWS"; line: 1, column: 3]

4. com.fasterxml.jackson.core.JsonParseException: Unrecognized token 'At': was expecting (JSON String, Number, Array, Object or token 'null', 'true' or 'false')
 at [Source: (String)"At line 80 ENDATA"; line: 1, column: 3]

every time that I rerun the code I will get another error ... total 4 type as you can see.

My condition is I need to run it on azure synapse analytics using azure notebook.

• Some part of code I change before run such as add a parenthesis for print() function.

If you have any suggestion or advice please tell me.

Many thanks !

Answer 1

To resolve this com.fasterxml.jackson.core.JsonParseException: Unrecognized token 'Welcome': was expecting (JSON String, Number, Array, Object or token 'null', 'true' or 'false') error, try either of these following ways:

As suggested by pchtsp:

• It seems Jackson package is trying to convert logs and throwing JsonParseException, pass msg=False

  model.solve(PULP_CBC_CMD(msg=False))

As suggested by Imolkova:

• This issue could be because of mismatch between versions of different Jackson packages, you can refer to Troubleshoot dependency version conflicts