I'm getting a non-integer (float) private key in Paillier encryption
Looks like you missed the note on wikipedia:


  Note that the notation ${\frac {a}{b}}$ does not denote the modular multiplication of $a$ times the modular multiplicative inverse of $b$ but rather the quotient of $a$ divided by $b$, i.e., the largest integer value $v\geq 0$ to satisfy the relation $a\geq vb$.


As a side note, to make key generation even simpler, there is another note on wikipedia you may be interested in:


  If using $p,q$ of equivalent length, a simpler variant of the above key generation steps would be to set $g=n+1,\lambda =\varphi (n)$, and $\mu =\varphi (n)^{{-1}}{\bmod  n}$, where $\varphi (n)=(p-1)(q-1)$.