Reading CSV as NumPy array in Python
This tutorial will discuss how to read data from a CSV file and store it in a numpy array.
Use numpy.genfromtxt()the function to read CSV data into a NumPy array
genfromtxt()The function is commonly used to load data from a text file. We can use this function to read data from a CSV file and store it in a numpy array. This function has many available parameters that make it easier to load the data in the desired format. We can use different parameters of this function to specify the delimiter, handle missing values, remove specified characters and specify the data type of the data.
For example,
from numpy import genfromtxt
data = genfromtxt("sample.csv", delimiter=",", skip_header=1)
print(data)
Output:
[[1. 2. 3.]
[4. 5. 6.]]
This leads to many other functions, such as recfromtxt()and recfromcsv(), which perform the same function but have different default values.
In the following code, we will use recfromcsv()File to read data from a CSV file.
import numpy as np
data = np.recfromcsv("sample.csv", skip_header=0)
print(data)
Output:
[(1, 2, 3) (4, 5, 6)]
Note that we did not have to specify the delimiter as a comma, nor did we have to specify other values to specify a header row.
Read CSV data into NumPy arrays using pandasdataframe
We can also make use of pandasDataFrame to read CSV data into an array. To do this, we read the data into a DataFrame and then convert it into an array using the function pandasfrom the library .values()numpy()
The following code achieves this.
from pandas import read_csv
df = read_csv("sample.csv")
data = df.values
print(data)
Output:
[[1 2 3]
[4 5 6]]
Use csvthe CSV module to read CSV data into a NumPy array
csvThe module is used to efficiently read and write data to CSV files. This method will use this module to read the data from the CSV file and store it in a list. We will then proceed to convert this list into a numpy array.
The following code will explain this.
import csv
import numpy as np
with open("sample.csv", "r") as f:
data = list(csv.reader(f, delimiter=";"))
data = np.array(data)
print(data)
Output:
[['1,2,3']
['4,5,6']]
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