For any purpose or purposes mentioned in this chapter, the council may enact and make all necessary ordinances, rules and regulations; and they may enact and make all such ordinances and rules, not inconsistent with the laws of the state, as may be expedient for maintaining the peace and good government and welfare of the city and its trade and commerce; and all ordinances may be enforced by prescribing and inflicting upon its inhabitants, or other persons violating the same, such fine not exceeding five hundred dollars, and such imprisonment not exceeding three months, or both such fine and imprisonment, as may be just for any offense, recoverable with costs of suit, together with judgment of imprisonment, until the fine and costs are paid or satisfied; and any person committed for the nonpayment of fine and costs, or either, may be compelled to work out the same as herein provided; but, in any case wherein the penalty for an offense is fixed by any statute, the council shall affix the same penalty by ordinance for the punishment of such offense, except that imprisonments, when made under city ordinances, may be in the city prison or workhouse instead of the county jail.