from qiskit import QuantumCircuit,QuantumRegister,ClassicalRegister

qc=QuantumCircuit(QuantumRegister(3,'qr'))
qc.h(0)
qc.h(1)
qc.h(2)
qc.draw(output="mpl")

qc=QuantumCircuit(QuantumRegister(3,'qr'))
qc.h(range(3))
qc.draw(output="mpl")

q=QuantumRegister(3,'qr')
qc=QuantumCircuit(q)
qc.h(q[0:3])
qc.draw(output="mpl")

q=QuantumRegister(3,'qr')
qc=QuantumCircuit(q)
qc.h(q[0])
qc.draw(output="mpl")