Add A 1-D Numpy Array to DataFrame as a Row

add numpy array to dataframe as column
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convert numpy.ndarray to series
assign array to dataframe

Is there a function which allows you to efficiently append a NumPy array directly to a DataFrame?


df = pd.DataFrame(columns=['col1', 'col2', 'col3'])

Out[1]: +------+------+------+
        | Col1 | Col2 | Col3 |
        |      |      |      |

arr = np.empty(3)

# array is populated with values. Random numbers are chosen in this example,
#    but in my program, the numbers are not arbitrary.
arr[0] = 756
arr[1] = 123
arr[2] = 452

Out[2]: array([756, 123, 452])

How do I directly append arr to the end of dfto get this?

| Col1 | Col2 | Col3 |
|  756 |  123 |  452 |

I've tried using df.append(arr) but it doesn't accept NumPy arrays. I could convert the NumPy array into a DataFrame then append it, but I think that would be very inefficient, especially over millions of iterations. Is there a more efficient way to do it?

@rafaelc comment can work only if your Pandas DataFrame is indexed from 0 to len(df)-1, so it is not a general workaround and it can easily produce a silent bug in your code.

If you are sure that your Numpy array has the same columns of your Pandas DataFrame you could try using the append function with a dict comprehension as follows:

data_to_append = {}
for i in range(len(df.columns)):
    data_to_append[df.columns[i]] = arr[i]
df = df.append(data_to_append, ignore_index = True)

You need to reassign the DataFrame because append function does not support in-place modification.

I hope it helps.

pandas.DataFrame.append, Append rows of other to the end of this frame, returning a new object. Columns not in this frame are added as new columns. Parameters: other : DataFrame or  Here is other example: import numpy as np import pandas as pd """ This just creates a list of touples, and each element of the touple is an array""" a = [ (np.random.randint(1,10,10), np.array([0,1,2,3,4,5,6,7,8,9])) for i in range(0,10) ] """ Panda DataFrame will allocate each of the arrays , contained as a touple element , as column""" df = pd.DataFrame(data =a,columns=['random_num

@BalrogOfMoira is that really faster than simply creating the dataframe to append?

df.append(pd.DataFrame(arr.reshape(1,-1), columns=list(df)), ignore_index=True)

Otherwise @Wonton you could simply concatenate arrays then write to a data frame, which could the be appended to the original data frame.

pandas.DataFrame, Two-dimensional size-mutable, potentially heterogeneous tabular data structure as_matrix([columns]), Convert the frame to its Numpy-array representation. Converting a 2D numpy array to dataframe rows. Ask Question Asked 2 years, 10 months ago. Active 2 years, 10 months ago. Add one row to pandas DataFrame. 1126.

This will work:


Intro to data structures, In [1]: import numpy as np In [2]: import pandas as pd Series is a one-​dimensional labeled array capable of holding any data type (integers, strings, floating point numbers, Python objects, etc.). The basic method to create a Series is to call: When the data is a dict, and columns is not specified, the DataFrame columns  So, the simple solution to the original question, from seven years ago, is to use vstack () to add a new row after converting the row to a numpy array. But a more realistic solution should consider vstack's poor performance under those circumstances.

Essential basic functionality, to_numpy() gives some control over the dtype of the resulting numpy.ndarray . For heterogeneous data (e.g. some of the DataFrame's columns are not all the d NaN 0.558688 -1.226343 In [45]: df.add(df2, fill_value=0) Out[45]: one two  Pandas DataFrame is two-dimensional size-mutable, potentially heterogeneous tabular data structure with labeled axes (rows and columns). This data structure can be converted to NumPy ndarray with the help of Dataframe.to_numpy() method. Syntax: Dataframe.to_numpy(dtype = None, copy = False) Parameters: dtype: Data type which we are passing like

Add numpy array as column to Pandas data frame, Using the below code: import numpy as np. import pandas as pd. import scipy.​sparse as sparse. df = pd.DataFrame(np.arange(1,10).reshape(3  Pandas DataFrame – Add or Insert Row. To append or add a row to DataFrame, create the new row as Series and use DataFrame.append() method. In this tutorial, we shall learn how to append a row to an existing DataFrame, with the help of illustrative example programs. Syntax – append() Following is the syntax of DataFrame.appen() function.

How to create Pandas DataFrame from a Numpy array in Python, A Pandas DataFrame is a two-dimensional data structure that can be created using the data from a NumPy array . with data set to a NumPy array, index set to a list of row names, and column set to a list column1 column2 row1 1 2 row2 3 4  Create a list of dictionaries in which each dictionary corresponds to an input data row. Create a data frame from this list. I had a similar task for which appending to a data frame row by row took 30 min, and creating a data frame from a list of dictionaries completed within seconds.

  • Use df.loc[len(df)] = arr
  • @rafaelc that's going to slow to a crawl very quickly. it starts to take 10ms per row once your at 100K rows and there's another 900K+ to go
  • @ALollz but not one said there was a for loop and we were appending at every iteration
  • can you give more information about how you're generating these numbers? Likely the best solution is going to be to preallocate everything, fill it accordingly and then construct the DataFrame at the end.
  • It's useful if the DataFrame already exists and populated with data.