Rather than running Python to generate a random number, we can use builtin features of Bash to do this more quickly and with less code.

RANDOM is a Bash variable that expands to a new random number in the range 0 to 32767 every time it is referenced.

{0..5} expands to the numbers 0 1 2 3 4 5.

${RANDOM:0:1} is the first digit of a random number.

let enables an arithmetic context in Bash. We initialize N to 0, generate 6 random digits multiplied by increasing powers of 10, effectively building a 6-digit random number:

𝑵 = 𝒙₁ + 10𝒙₂ + 100𝒙₃ + 1000𝒙₄ + 10000𝒙₅ + 100000𝒙₆

where 𝒙ᵢ are the 6 initial digits taken from the 6 calls to $RANDOM.

This method doesn't preclude the possibility of leading zeroes counting towards the 6-digit total.