for in lstq enqueue( lst [ while not isempty()lst append( dequeue() if lst !lstprint("test failed"elseprint("test passed" tryq dequeue(print("test failed" except runtimeerrorprint("test passed"exceptprint("test failed" tryq front(print("test failed" except runtimeerrorprint("test passed"exceptprint("test failed" if __name__=="__main__"main(infix expression evaluation an infix expression is an expression where operators appear in between their operands for example( is an infix expression because appears between the and and appears between its operands pythonbeing programming languagecan evaluate infix expressions howeverlet' say we would like to write program that would evaluate expressions entered by the user can we do this in python programit turns out we canand very easily python includes function that will treat string like an expression to be evaluated and will return the result of that evaluation the function is called eval here is program that uses the eval function def main()expr input("please enter an infix expression"result eval(exprprint("the result of",expr,"is",result if __name__ ="__main__"main(this copy belongs to 'acha