How can I merge three columns into one column according to the order of in the three columns

Could you give me an advice, please?

I have three columns, e.x.:

x     y     z
0.2   0.5   0.26
0.75  0.58  0.25
0.78  0.86  0.95
0.56  0.75  0.52
0.45  0.47  0.57
0.2   0.58  0.98

Result: And I need only one column with this sequence:

    xyz
x1  0.2
y1  0.5
z1  0.26
x2  0.75
y2  0.58
z2  0.25
... 0.78
    0.86
    0.95
    …

I didn´t find a similar problem... Thank You very much. I tried to use "dcast" (R) or "concat" (Python) but I am stack.

Solution

You can use pd.melt and create the row names you want with np.tile:

m = df.T.melt(value_name='xyz')
rows = np.tile(df.columns, df.shape[0])
m['variable'] = rows.tolist() + (m.variable + 1).astype(str)

    variable   xyz
0        x1  0.20
1        y1  0.50
2        z1  0.26
3        x2  0.75
4        y2  0.58
5        z2  0.25
6        x3  0.78
7        y3  0.86
8        z3  0.95
9        x4  0.56
10       y4  0.75
11       z4  0.52
12       x5  0.45
13       y5  0.47
14       z5  0.57
15       x6  0.20
16       y6  0.58
17       z6  0.98

And if you want is as index do:

m.set_index('variable')