Is it possible to append to an empty data frame that doesn't contain any indices or columns?
I have tried to do this, but keep getting an empty dataframe at the end.
e.g.
import pandas as pd
df = pd.DataFrame()
data = ['some kind of data here' --> I have checked the type already, and it is a dataframe]
df.append(data)
The result looks like this:
Empty DataFrame
Columns: []
Index: []
This should work:
>>> df = pd.DataFrame()
>>> data = pd.DataFrame({"A": range(3)})
>>> df = df.append(data)
>>> df
A
0 0
1 1
2 2
Since the append doesn't happen in-place, so you'll have to store the output if you want it:
>>> df = pd.DataFrame()
>>> data = pd.DataFrame({"A": range(3)})
>>> df.append(data) # without storing
>>> df
Empty DataFrame
Columns: []
Index: []
>>> df = df.append(data)
>>> df
A
0 0
1 1
2 2
FutureWarning: The frame.append method is deprecated and will be removed from pandas in a future version. Use pandas.concat instead.
And if you want to add a row, you can use a dictionary:
df = pd.DataFrame()
df = df.append({'name': 'Zed', 'age': 9, 'height': 2}, ignore_index=True)
which gives you:
age height name
0 9 2 Zed
FutureWarning: The frame.append method is deprecated and will be removed from pandas in a future version. Use pandas.concat instead.You can concat the data in this way:
InfoDF = pd.DataFrame()
tempDF = pd.DataFrame(rows,columns=['id','min_date'])
InfoDF = pd.concat([InfoDF,tempDF])
The answers are very useful, but since pandas.DataFrame.append was deprecated (as already mentioned by various users), and the answers using pandas.concat are not "Runnable Code Snippets" I would like to add the following snippet:
import pandas as pd
df = pd.DataFrame(columns =['name','age'])
row_to_append = pd.DataFrame([{'name':"Alice", 'age':"25"},{'name':"Bob", 'age':"32"}])
df = pd.concat([df,row_to_append])
So df is now:
name age
0 Alice 25
1 Bob 32
pandas.DataFrame.appendDeprecated since version 1.4.0: Useconcat()instead.
Therefore:
df = pd.DataFrame() # empty dataframe
df2 = pd..DataFrame(...) # some dataframe with data
df = pd.concat([df, df2])
Why am I getting "AttributeError: 'DataFrame' object has no attribute 'append'?
append has been removed, use pd.concat instead.The idiomatic way to append DataFrames (it to collect all your smaller DataFrames into a list, and then make one single call to pd.concat.
df_list = []
for df in some_function_that_yields_df():
df_list.append(df)
big_df = pd.concat(df_list)
The rationale for its removal was to discourage iteratively growing DataFrames in a loop (which is what people typically use append for). This is because append makes a new copy at each stage, resulting in quadratic complexity in memory. See Creating an empty Pandas DataFrame, and then filling it (in particular, this answer) where answers discourage iteratively growing DataFrames.
More info:
newDF = pd.DataFrame() #creates a new dataframe that's empty newDF = newDF.append(oldDF, ignore_index = True) # ignoring index is optionalprint(df.append(data)), becauseappend()always returns None in Pythonappendwas silently removed from the API to discourage people from iteratively growing DataFrames inside a loop :Dappendinside a loop is quadratic memory usage, so the suggested approach is to accumulate individual rows or DataFrames inside a python list and then convert it into one big df at the end. More information in my answer