I simply want to add data frames that are stored in a dictionary. intuitively I would want to loop the dictionary. However I do not have an initial dataframe with zero values. What is the best way to accomplish that elegantly. Currently I am doing the following:
dict = {'B' :df1, 'C':df2, 'D': df3}
total = dict['B'] + dict['C'] + dict['D']
the dfs are initialized from reading from a csv file and there could be more than 3.
How can I accomplish this in a loop?
You can pass the dict values to concat, example:
In [195]:
d = {}
d['a'] = pd.DataFrame({'a':np.arange(5)})
d['b'] = pd.DataFrame({'b':np.arange(5)})
total = pd.concat(d.values(), axis=1)
total.sum()
Out[195]:
a 10
b 10
dtype: int64
Assuming you want to add (and not concatenate as shown in another answer) these DataFrames you could use something like the following:
#!/usr/bin/env python3
# coding: utf-8
import pandas as pd
import numpy as np
df1 = pd.DataFrame(np.random.rand(3,2))
df2 = pd.DataFrame(np.random.rand(3,2))
df3 = pd.DataFrame(np.random.rand(3,2))
df4 = pd.DataFrame(np.random.rand(3,2))
d = {'a': df1, 'b': df2, 'c': df3, 'd': df4}
total = 0
for key, df in d.items():
total += df
total and edited my answer accordingly. Sorry for that.NameError telling you that a variable (in this case total is not defined). Did I solve your main problem concerning the addition of dataframes?You could create a panel and then sum:
pd.Panel(dict).sum()
On a side note, it's not best practice to overwrite the inbuilt dict function
just for completeness, here is what demonstrates the problem and the solution:
import pandas as pd
import numpy as np
df1 = pd.DataFrame(np.random.rand(3,2))
df2 = pd.DataFrame(np.random.rand(3,2))
df3 = pd.DataFrame(np.random.rand(3,2))
df4 = pd.DataFrame(np.random.rand(3,2))
d = {'a': df1, 'b': df2, 'c': df3, 'd': df4}
for key, df in d.items():
if 'total' in locals():
print("found")
total += df
else:
print("not")
total = df
print(total)
del total
