Plus state $\lvert +\rangle$ implementation using Qiskit. The $\lvert +\rangle$ state is prepared by applying a Hadamard gate to $\lvert 0\rangle$.

from qiskit import QuantumCircuit
from qiskit.quantum_info import Statevector
 
qc = QuantumCircuit(1)
qc.h(0)  # |0> -> |+> = (|0> + |1>) / sqrt(2)
print(Statevector(qc))
# Statevector([0.70710678+0.j, 0.70710678+0.j], dims=(2,))