I am trying to loop through an Excel sheet and append the data from multiple sheets into a data frame. 

So far I have: 

```
master_df = pd.DataFrame()
for sheet in target_sheets:
    df1 = file.parse(sheet, skiprows=4) 
    master_df.append(df1, ignore_index=True)

```

But then when I call `master_df.head()` it returns `__`

The data on these sheets is in the same format and relate to each other. 

So I would like to join them like this: 

Sheet 1 contains: 

```
A1
B1
C1

```

Sheet 2 contains: 

```
A2
B2
C2

```

Sheet 3:

```
A3
B3
C3

```

End result: 

```
A1
B1
C1
A2
B2
C2
A3
B3
C3

```

Is my logic correct or how can I achieve this?