Need to get length of data frame stored in elements of list in python pandas

Question

This problem can be solved by using different variable names in the loop. However, I need to check whether we can find the length of elements of List which can store data frames.

I have written code to read all .csv file stored in a folder. I have created the list containing the characters. Now, I am reading one by one csv files from a folder and storing as data frames in elements of list. Hence, all Elements of list contain data frame which is obtained by reading csv files. I.e., List element 0 - "a" contain one data frame, List element 1 - "b" contain other data frames and so on. I need to find the length of Data frames contained by elements of the list. I am using len(), but this reflects the only length of the list. Kindly suggest me some solution.

Below mentioned is the code.

url = "C:/Users/SONY/Desktop/SEdge/Proec/Day/Master Files/20-12-2017/"

count = 0;

lst = ["a", "b", "c", "d"]

os.chdir(url)

for file in glob.glob("*.csv"):

    join = url + file;

    lst[count] = pd.read_csv(join)

    count +=1;

print(len(lst[1]))

Possible duplicate of How do you create different variable names while in a loop? (Python) — Bharath M Shetty
– Bharath M Shetty, Commented Dec 22, 2017 at 6:27
You are not suppose to store data in a string, they are called variables. Though there is a dtype called dictionary to do exactly what you want. A bit more understanding of data structrures is required from your side. — Bharath M Shetty
– Bharath M Shetty, Commented Dec 22, 2017 at 6:29
I have no clue why you're filling a list with a, b, c, d and then subsequently replacing it with something else. Why not just create an empty list and then use list.append? — cs95
– cs95, Commented Dec 22, 2017 at 6:32
@cᴏʟᴅsᴘᴇᴇᴅ perhaps a misunderstanding of dictionary over a list. — Bharath M Shetty
– Bharath M Shetty, Commented Dec 22, 2017 at 6:33
@sonismit Why not find the length as you read it? df = pd.read_csv(join); print(len(df)); di[lst[count]] = df — cs95
– cs95, Commented Dec 22, 2017 at 6:39

Alexandre Jacobs · Accepted Answer · 2017-12-22 07:00:03Z

2

You cant store data in a string. You have to store them in a variable. Since you are looping over a bunch of csv file the opt data structure is dictionary. i.e

An improvement of your own code :

lst = ['a','b','c','d']
di = {} 

for count, file in enumerate(glob.glob("*.csv")):
    join = url + file;
    di[lst[count]] = pd.read_csv(join)

di['a'] stores the first csv file. Similarly di['b] the second one and so on.

Now if you do len(di[lst[1]]) this will give you the length of the csv file 1.

For more details about datastructures I suggest you to go through the documentation

edited Dec 22, 2017 at 7:00

Alexandre Jacobs

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answered Dec 22, 2017 at 6:36

Bharath M Shetty

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5 Comments

cs95 Over a year ago

Use enumerate so you don't need an external count variable.

Bharath M Shetty Over a year ago

@cᴏʟᴅsᴘᴇᴇᴅ there are so many improvements that can be done here. I leave it to OP with this.

soni smit Over a year ago

@Dark I am not clear about how to use enumerate. Can you provide me code line with this? Thanks in advance.

soni smit Over a year ago

@Dark... Got it. Thanks. enumerate is useful when we need to increment counter itself. I will assign values to both count and files.

Bharath M Shetty Over a year ago

You got it. Happy coding. You will love python for this

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