At this point the syntax error you are most likely to make is an illegal variable name, like class and yield, which are keywords, or
US$, which contain illegal characters.
If you put a space in a variable name, Python thinks it is two operands without an operator:
>>> bad name = 5 SyntaxError: invalid syntax
For syntax errors, the error messages don’t help much. The most common messages are
SyntaxError: invalid syntax and
SyntaxError: invalid token, neither of which is very informative.
The runtime error you are most likely to make is a “use before def;” that is, trying to use a variable before you have assigned a value. This can happen if you spell a variable name wrong:
>>> principal = 327.68 >>> interest = principle * rate NameError: name 'principle' is not defined
Variables names are case sensitive, so
LaTeX is not the same as
At this point the most likely cause of a semantic error is the order of operations. For example, to evaluate
1/2π, you might be tempted to write
>>> 1.0 / 2.0 * pi
But the division happens first, so you would get
π / 2, which is not the same thing! There is no way for Python to know what you meant to write, so in this case you don’t get an error message; you just get the wrong answer.