No, perfect voltage sources nor perfect current sources exist. Everything has what might be called as output impedance (or Z). Think of output Z like a hypothetical but apparent phantom resistor in series with the output from some ideal voltage source. Sometimes this may even be called ESR, or Equivalent Series Resistance. Something that has a really low output Z would act like a voltage source, such as big lead acid batteries or LiPo's, for example. Something that has a really high output Z (approaching infinity in fact) would act more like a current source. In fact, if you had a supply voltage that was approaching infinity and the Z that was some multiple of that voltage, then you would indeed have a "ideal" theoretical current source based on the ratio of that voltage to that Z. However, most real-world supplies are neither, as they have some finite voltage output and output Z, as Infinity and zero resistance to not really exist. the idea of Z in this sense is more of a mathimatical concept than anything but it's useful to understand this in power supply design, impedance matching or bridging, and many other things. In fact, the same core concepts apply to ALL forms or energy, let it be thermal (temperature, heat, and thermal resistance), fluid-dynamics (pressure, flow, and backpressure), etc etc etc.You can just as easily configure a power supply to have a "constant current" output or "constant voltage" output, or even both, where when the load attempts to draw more current than the power supply current limit is set to, the voltage will sag such that the current is regulated to what has been set. In fact, this is what most lab power supplies do! Just set the maximum voltage and maximum current limits and whether if it is in CV or CC mode depends on the input Z of the load!