create dictionary with for loop (python)

Question

cols = 'ABC'
ind = range(3)

value=[]

dic = {}

for c in cols:
        for i in ind:
            value.append(str(c) + str(i))
        dic[c] = value

print(dic)

output:

{'A': ['A0', 'A1', 'A2', 'B0', 'B1', 'B2', 'C0', 'C1', 'C2'], 'B': ['A0', 'A1', 'A2', 'B0', 'B1', 'B2', 'C0', 'C1', 'C2'], 'C': ['A0', 'A1', 'A2', 'B0', 'B1', 'B2', 'C0', 'C1', 'C2']}

why am i getting the above output ?

while I want the output to be like

output:

{'A': ['A0', 'A1', 'A2'], 'B': ['B0', 'B1', 'B2'], 'C': ['C0', 'C1', 'C2']}

Boseong Choi · Accepted Answer · 2020-04-08 15:06:41Z

3

Because you used same object value for every values.
You should insert value = [] in the for c in cols: block,
But here is more pythonic way:

cols = 'ABC'
ind = range(3)

dic = {
    c: [c + str(i) for i in ind]
    for c in cols
}
print(dic)

output:

{'A': ['A0', 'A1', 'A2'], 'B': ['B0', 'B1', 'B2'], 'C': ['C0', 'C1', 'C2']}

answered Apr 8, 2020 at 15:06

Boseong Choi

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1 Comment

Mayank S Over a year ago

I am learning the list and dictionary comprehension, so i was trying to code first in old way. Thank you for highlighting to the reset value.

Sundeep · Accepted Answer · 2020-04-08 15:07:56Z

0

Thats simple you have to reset you array after each iteration

cols = 'ABC'
ind = range(3)
dic = {}
for c in cols:
    value=[]
    for i in ind:
        value.append(str(c) + str(i))
    dic[c] = value
print(dic)

Result:

{'A': ['A0', 'A1', 'A2'], 'B': ['B0', 'B1', 'B2'], 'C': ['C0', 'C1', 'C2']}

answered Apr 8, 2020 at 15:07

Sundeep

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1 Comment

Mayank S Over a year ago

Thank you for answering the question

Ahmed Soliman · Accepted Answer · 2020-04-08 15:09:02Z

0

cols = 'ABC'
dic = {c:[c + str(x) for x in range(3)] for c in cols}

print(dic)

Output:

{'A': ['A0', 'A1', 'A2'], 'B': ['B0', 'B1', 'B2'], 'C': ['C0', 'C1', 'C2']}

answered Apr 8, 2020 at 15:09

Ahmed Soliman

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Comments

David Medinets · Accepted Answer · 2020-08-23 00:09:41Z

-1

def make_df(cols, ind):          
    # Create a DataFrame           
    data = {c: [str(c) + str(i) for i in ind] for c in cols}
    return pd.DataFrame(data, ind)

# Example DataFrame       
make_df('ABC', range(3))

edited Aug 23, 2020 at 0:09

David Medinets

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answered Aug 22, 2020 at 17:36

yogesh ramesh

1

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