Run a loop to generate variable names in Python

Question

I'm trying to import datasets which have the following filenames (phone1, phone2, etc)

df1 = pd.read_csv(r'C:\Users\...\phone1.csv')
df2 = pd.read_csv(r'C:\Users\...\phone2.csv')
df3 = pd.read_csv(r'C:\Users\...\phone3.csv')
df4 = pd.read_csv(r'C:\Users\...\phone4.csv')
df5 = pd.read_csv(r'C:\Users\...\phone5.csv')
df6 = pd.read_csv(r'C:\Users\...\phone6.csv')

I tried the following code

for i in range(1, 7):
    'df'+i = pd.read_csv(r'C:\Users\siddhn\Desktop\phone'+str(i)+'.csv', engine = 'python')

But I get an error saying that cannot assign to operator

How to import the datasets using a loop.?

Don't do that. Instead, create a list `dfs = []` and use `dfs.append( pd.read_csv(...) )`. Now, you can use `dfs[0]` to refer to one specifically, but you can loop through them easily using `for df in dfs:`. — Tim Roberts, Jun 19 '21 at 04:54
As @TimRoberts mentioned you can store your DataFrames in list, but if it essential for your DataFrames to have specific names, using dict in a loop also possible. Something like that could be made (inside your for loop): dfs[f"df_{i}"] = pd.read_csv(...) — Antonio Margaretti, Jun 19 '21 at 04:58

Corralien · Answer 1 · 2021-06-19T05:22:38.907

2

As @TimRoberts mentioned, you should use a list or a dictto store your dataframes but if you really want to have variable df1, df2, ..., df6, you can use locals() or globals():

for i in range(1, 7):
    locals()[f'df{i}'] = pd.read_csv(fr'C:\Users\siddhn\Desktop\phone{i}.csv')

print(df1)
print(df2)

edited Jun 19 '21 at 05:22

answered Jun 19 '21 at 05:09

Corralien

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While using `locals()` may solve your problem, it will make your code messy and difficult to comprehend. – Vishnudev Krishnadas Jun 19 '21 at 05:29
1

@Vishnudev. I'm totally agree with you – Corralien Jun 19 '21 at 06:08

cbrr09 · Answer 2 · 2021-06-19T05:13:33.547

1

you can store it in a list, here is the idea

var = []
for i in range(1, 7):
    var.append(i)

print(var[0])
print(var[2])

and from the list you can access the value using their key.

edited Jun 19 '21 at 05:13

answered Jun 19 '21 at 05:05

cbrr09

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Vishnudev Krishnadas · Accepted Answer · 2021-06-27T05:03:50.167

1

Use the inbuilt glob package

from glob import glob

fullpath = f'C:\Users\siddhn\Desktop\phone[1-6].csv'
dfs = [pd.read_csv(file) for file in glob(fullpath)]

print(dfs[0])

edited Jun 27 '21 at 05:03

answered Jun 19 '21 at 05:23

Vishnudev Krishnadas

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score 0 · Answer 4 · answered Jun 19 '21 at 05:02

'df'+i return a lvalue, i.e that can be assigned to other variables but cannot store some contents. insted of using

for i in range(1, 7):
    'df'+i = pd.read_csv(r'C:\Users\siddhn\Desktop\phone'+str(i)+'.csv', engine = 'python')

create a List of data_frames as df = [] Now append your data_frames as

for i in range(7):
   df.append(pd.read_csv(r'C:\Users\siddhn\Desktop\phone'+str(i)+'.csv', engine = 'python')

You can then acess data_frames by indexing them like df[0] or df[1].....

score 0 · Answer 5 · answered Jun 19 '21 at 05:08

You can create a list of data frames and then iterate over it or access by index.

df_list = [pd.read_csv(r'C:\Users\siddhn\Desktop\phone'+str(i)+'.csv', engine = 'python') for i in range(1, 7)]
df_list[1]

The variable cannot be an operator thats the reason you get the error.

Run a loop to generate variable names in Python

5 Answers5