[Solved:] How to use pd.append() ?

[ju21878436312]

Can someone tell me, why the first example of how to use pd.append() works, and the second not?

# 1) This works fine: 

df1 = pd.DataFrame([[1, 2], [3, 4]], columns=list('AB'))
df2 = pd.DataFrame([[5, 6], [7, 8]], columns=list('AB'))
df1.append(df2)
df1

# 2) However this does not work:

d3 = {'1':[100],'pos':["middle"]}
d4 = {'1':[200],'pos':["middle"]}

df3 = pd.DataFrame(data=d3)
df4 = pd.DataFrame(data=d4)

df3.append(df4)
df3

I am using the 2nd way to create my dataframe, and prefer to combine my dataframes with

pd.append() 

instead of

pd.concat()