What is the difference between python string concatenation and string insertion

I want to know wha开发者_Python百科t is the diff between two string operations in python

filestamp = time.strftime('%Y-%m-%d')
database = "mysql";

Between this

filename = "/home/vmware/%s-%s.sql" % (database, filestamp)

and

filename = "/home/vmware/"+database+"-"+filestamp+".sql"

String interpolation using the '%' operators take the types of the interpolated values into account. String concatentation using the '+' will only work for strings. So you can't mix strings with numbers using the '+' operator. In general: string interpolation is what you want - at least for building strings from other values especially if you deal with different types.

The first approach creates 1 string where as the second creates temporary strings which is wasted. Strings in python are immutable, once created you cannot modify it.