integer division
Pythonは型を明示的に定義しないので，見落としがちだ．
tsz=100
tszinv=1/tsz
として，tszinv=0.01を期待すると，実はtszinvはゼロになってしまう．これは整数同士の演算結果は整数になるためだ．実数で演算結果を得るには
tszinv=1/float(tsz)
とすればよい．
tsz=100
tszinv=1/tsz
If you expect tszinv=0.01, it is wrong. Actually, tszinv=0. This is because the operation between integers results in an integer. In order to get a floating result, you should write
tszinv=1/float(tsz)
In python, we usually do not declare types of variables, and tend to overlooks this kind of mistakes.