How to run for loop in pandas

Question

I am doing a coursera course and want to create various dataframe using for loop, the idea is to create a list and then add each df into the list. However, below come back with error:

File "<ipython-input-10-2863e455a5c5>", line 7
    array.append(county_df.where(county_df['STNAME']=state))
                                ^
SyntaxError: keyword can't be an expression

census_df = pd.read_csv('census.csv')
county_df=census_df[census_df['SUMLEV'] == 50]
county_df.head()
county_df['STNAME'].unique()
list = []
print type(list)
for state in county_df['STNAME'].unique():
    array.append(county_df.where(county_df['STNAME']=state))

print (list)

I think this is a duplicate of stackoverflow.com/q/11633421/1240268 — Andy Hayden
– Andy Hayden, Commented Nov 6, 2017 at 1:32

BENY · Accepted Answer · 2017-11-06 01:34:32Z

1

In pandas we usually do this ..

l=[]

for _, df1 in county_df.groupby('STNAME'):
    l.append(df1)

You code error

county_df['STNAME']=state)

should be

county_df['STNAME']==state)

And base on my understanding

county_df.loc[county_df['STNAME']==state,:]

edited Nov 6, 2017 at 1:34

answered Nov 6, 2017 at 1:19

BENY

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3 Comments

Andy Hayden Over a year ago

can also do with a list comprehension :)

Andy Hayden Over a year ago

This doesn't explain the keyword can't be an expression hmmm

Andy Hayden Over a year ago

Ah, gotcha, so county_df['STNAME'] is trying to be passed as a keyword argument to .where

Data Miner · Accepted Answer · 2017-11-06 02:30:55Z

0

I always convert my Pandas DataFrame to list by:

my_dataframe.values.tolist()

answered Nov 6, 2017 at 2:30

Data Miner

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