how to merge data frames with same format in python

Question

Looked at other similar questions, but none has the use case I have. I have multiple files with the same format and no header

file1
id, value 
1, 100
2, 150 
...

file2
10, 500
11, 510
....

I would like to "merge" them to have

id, value
1, 100
2, 150
...
10, 500
11, 510
...

tried merge, append, concat but couldn't achieve the end result I am looking for.

df2 = pd.DataFrame(columns=['id','value'])
df2.columns = ['id','value']
for file_name in os.listdir(work_dir):
    df1 = pd.read_csv(work_dir+'/'+file_name, header=None)
    df1.columns = ['id','value']
    df2 = pd.merge(df2,df1, on ='id')

Or any other suggestion to load multiple files in to a data frame appreciated. I do have another data frame coming from a db will be merged same way so merge is a question too.

Answer 1

You are looking for append. Try this:

df1.append(df2)

Answer 2

concat should also work for you. https://pandas.pydata.org/pandas-docs/stable/merging.html

You should also name each column upon import...

pd.read_csv(work_dir+'/'+file_name, header=None, names=['id', 'value'])

See Concatenate rows of two dataframes in pandas