A should be simple graphical function

Have you looked at PyPlot? It can do what you want, but it is a programming tool, which you may be more comfortable with. http://matplotlib.org/gallery.html

As for Excel, you need to use a line plot. Let's say you have your data like this:
London 0 1 2 8 4
NewYork 0 3 5 6 8
Paris 0 1 3 4 9

The first column of 0 is required and is your 'dummy' row so that your y-axis starts at 0.
Plot that data as a line plot with markers. You may need to hit the 'Switch Row/Column' button in the Chart Tools->Design tab. That should put the city labels along the x-axis and then have the appropriate points above each one. Now you need to get rid of the lines and make the markers into whatever you want (I chose orange dots). You will need to right click each line (series) and then choose to have no line and change the marker to what you want. That is tedious. I wrote a quick macro that will go through each series of the active chart and do that for you:

Sub LineChange()
Dim ser As Series

For Each ser In ActiveChart.SeriesCollection
    ser.Format.Line.Visible = msoFalse
    ser.MarkerStyle = 8
    ser.MarkerSize = 6
    ser.Format.Fill.Solid
    ser.Format.Fill.ForeColor.ObjectThemeColor = msoThemeColorAccent6
Next
    
End Sub

I wrote that code with no real error recovery or intelligence. You MUST select the chart you want to change (just click on it) and then run the macro. You will then need to do the manual task of right-clicking on the markers on the x-axis (i.e. the 0's) and making the markers 'None'.

I have attached a sample spreadsheet (with the macro - called LineChange) to get you started.

Note: to run macros you probably need to enable the 'Developer Mode' in Excel. Google the web and you will find a website with pretty pictures to show you how.