How set a particular cell value in pandas?

Question

I am trying to set a value in panda dataframe.

ZEROS = np.zeros((4,4), dtype=np.int)

df = pd.DataFrame(ZEROS,  columns=['A1','B1','C1','D1'])
df.at[2,3] = 32
df

I don't want NaN for the entire column, the expected output is below:

Using numpy I am able to set the value like below

ZEROS[1][3] = 44

output:

array([[ 0,  0,  0,  0],
       [ 0,  0,  0, 44],
       [ 0,  0,  0,  0],
       [ 0,  0,  0,  0]])

Answer 1

Use pd.DataFrame.iat to reference and/or assign to the ordinal location of a single cell.

ZEROS = np.zeros((4,4), dtype=np.int)

df = pd.DataFrame(ZEROS,  columns=['A1','B1','C1','D1'])
df.iat[2,3] = 32
df

   A1  B1  C1  D1
0   0   0   0   0
1   0   0   0   0
2   0   0   0  32
3   0   0   0   0

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You could also use iloc however, iloc can also take array like input. This makes iloc more flexible but also requires more overhead. Therefore, if it is only a single cell you want to change... use iat

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Also see this post for more information

loc/iloc/at/iat/set_value