From the previous example, we know that after we assign a value to x, we can use x, which means that x is now defined in the sense of other computer languages such as FORTRAN and C/C++. The opposite is also true, that we could not use X if it is not assigned a value in Python. In other words, when we assign a value to X, we have to define it first. Compared to languages such as C++ or FORTRAN, we don't have to define x as an integer before we assign 10 to it.

Another advantage is that we could change the data type of a variable easily. For the FOTRAN language, if we have defined x as an integer, we cannot assign a string to it. Since there is only assignment in Python, we could assign any value to a variable. For example, we could assign 10 to x. It is legal to assign a string, such as Hello World, to x in the next minute. However, we should not be confused with the data type conversion, such as converting an integer to a string or vice versa. Conversion between different data types will be discussed in the later chapters.