When simulating a quantum circuit using
qasm_simulator, the qubits that you assigned to the quantum circuit can be connected to all other qubits, or say, if there are $n$ qubits in the quantum circuit, for a single qubit it can interact with all other $n-1$ qubits.
This is quite an unpractical hypothesis for real quantum computation. k-local is a common criterion for a quantum computer and the only quantum computer I know that have full qubit-connectivity is this one(apparently I omitted the trivial case, single- or two-qubit quantum computer). In the case of quantum devices that IBM provided online access, e.g., 5-qubit ibmq_santiago, 5-qubit ibmq_5_yorktown, and 15-qubit ibmq_16_melbourne, all provided limited qubit connectivity.
So here arises my question: when designing a quantum circuit we have to take qubit connectivity into consideration, but how
qiskit works at this phase? Does it assign the job automatically(so the quantum circuit can still work), or should I pre-assign my logical qubits to the real qubits of the IBM quantum computer one-by-one(and if so, how?)?