Dynamic typing aka type inferencing (like in Python, but also in Java and C# when you use "var") can get you in trouble quickly. Consider this code:

   var fireable = someMethod();
   firable.fire();

The programmer intended this code to fire an employee. Let's say this code is in a military application, and another programmer modified the someMethod() function to return a missile. As long as the missile object has a fire() method this code will compile just fine... and do something the code didn't intend to do, i.e., fire a missile!

How likely are you to have employee firing and missile firing in the same program? Not very likely, but the principle is valid, nonetheless. You need to express your intention more clearly like this:

   Employee fireable = someMethod();

Now if someMethod() is modified to return a missile you get a compilation error, and the world will be a lot safer. You don't want missiles being fired by accident!