The safety standard in Tunisia is very high, even higher than in many western countries. And there are several reasons:

Tunisia is, according to its constitution, a democratic state, but actually, it is more of a presidential oligarchy in which the President ultimately decides the fate of the State, and in doing so, he is utilizing a network of affiliated persons and institutions. As is is usual in such systems, there are extensive monitoring and control structures, which reach deep into the lives of individual citizens and are expressed by a high police presence, meticulous information gathering, frequent vehicle checks and a strict control of members of the opposition.

Especially in tourist areas, the police is  omnipresent - they are controlling vehicles on almost every road intersection (in uniform), they can be found at each nightclub entrance (in civil), and there are as well patrols (uniformed and civilian) on beaches and in tourist zones. Moreover, a number of  persons belonging to the police apparatus will, at any time, most likely be "in the crowd" as well.

The main reason why they are there is not to control tourists, but to monitor the natives and keep track of where and what they are doing.
Since tourism is the main industry in Tunisia, the police will also ensure that no serious harassment of and attacks on tourists take place; any penalties are comparatively draconian and offer a high deterrent effect.

As a result, the tourist zones are extremely safe, but this does, of course, not mean that handbag theft or fraud in shops, for example, will not take place if one is not cautious. Physical attacks on tourists are, though, highly unlikely, unless they are provoked (starting a fight, etc.). The murder and rape rate on tourists is next to nothing, but both can happen in very rare cases nevertheless.

Especially at night in unlit and lonely places, even in the tourist zone, one should be cautious - but this behaviour is recommended in almost all areas in the whole world as well.

One should refrain from nocturnal solitary hikes on the roads or walks along the beach. One should abstain from heavy drinking in clubs that are frequented mainly by locals.

On walks in the day, one should not carry handbags (instead use belly bags, belt bags, inside pockets of jackets) - and do not brag with expensive jewelry.

Large sums of money should never been carried around or even shown to anyone at all.

A special problem is the abuse of alcohol of tunisian men in the tourist zones. Granted, it happens to a much lesser extent than in some western countries, but the "drinking stamina" is also significantly lower - and the social acceptance among locals is very low to absent.

As a rule of thumb, one should generally refrain from hanging around with individuals and groups who drink more than small amounts (1-2 glasses) of alcohole.