TypeError: 'str' object is not callable (Python)

This is the problem:

global str

str = str(mar)

You are redefining what str() means. str is the built-in Python name of the string type, and you don't want to change it.

Use a different name for the local variable, and remove the global statement.

While not in your code, another hard-to-spot error is when the % character is missing in an attempt of string formatting:

"foo %s bar %s coffee"("blah","asdf")

but it should be:

"foo %s bar %s coffee"%("blah","asdf")

The missing % would result in the same TypeError: 'str' object is not callable.

In my case I had a class that had a method and a string property of the same name, I was trying to call the method but was getting the string property.