CODEWITHSUNDEEP
pythonpython-3.xcsv
idkfa
idkfa

Reputation: 158

Import of csv data rows and columns when specyfing delimiter

import csv
import matplotlib.pyplot as plt

filename = r"C:\Users\name\Desktop\sampledata.csv"

with open(filename, newline='') as file:
    reader = csv.reader(file)
    header = next(reader)
    data = []   
    for row in reader:
        measured_time = float(row[0])
        wv1 = float(row[1])
        wv2 = float(row[2])
        data.append([measured_time, wv1,wv2])

time=data[0]
y1=data[1]

plt.plot(time,y1)

plt.show()

Works just fine, but as this was a test before I work with the real data.

Now the real data doesn't have a header and consists on only 2 columns.

import csv
import matplotlib.pyplot as plt

filename = r"C:\Users\name\Desktop\real_data.csv"

with open(filename, newline='') as file:
    reader = csv.reader(file,delimiter=';')
    data = []   
    for row in reader:
        measured_time = float(row[0])
        wv1 = float(row[1])
        data.append([measured_time, wv1])

time=data[0]
y1=data[1]

plt.plot(time,y1)

plt.show()

this yields

time=[100,1]

y1=[110,2]

so basically just the first 2 rows while the first codeblock correctly extracts the columns

time=[100 110 ...]

y1=[1 2 ...]

The same thing happens when I use

import csv
import matplotlib.pyplot as plt

filename = r"C:\Users\name\Desktop\sampledata.csv"

with open(filename, newline='') as file:
    reader = csv.reader(file)
    header = next(reader)
    data = []   
    for row in reader:
        measured_time = float(row[0])
        wv1 = float(row[1])
        data.append([measured_time, wv1])

time=data[0]
y1=data[1]

plt.plot(time,y1)

plt.show()

For now my workaround is

data = np.array(data).astype("float")


time=data[:,0]
y1=data[:,1]

Surely there has to be a better way, I'm just starting with Python.

Data used:

sample data
Time,279 nm,306 nm
0,100,150
1,110,175
2,125,230
3,130,245

real data
3.986931e+002;0.000000e+000
4.021733e+002;0.000000e+000

Upvotes: 0

Views: 135

Answers (1)

Adirio
Adirio

Reputation: 5286

list(zip()) allows to traspose a set of sequences:

time = [100, 1]
y1 = [110, 2]
l = list(zip(time, y1))
print(l) # [(100, 110), (1, 2)]
time = l[0] # (100, 110)
y1 = l[1] # (1, 2)

They are tuples that you can use as lists or you can transform them to lists:

time = list(l[0]) # [100, 110]
y1 = list(l[1]) # [1, 2]

If you want to get them straight into the opposite form you could swap the reading part:

import csv
import matplotlib.pyplot as plt

filename = r"C:\Users\name\Desktop\sampledata.csv"

with open(filename, newline='') as file:
    reader = csv.reader(file)
    # header = next(reader)
    time = []
    y1 = []   
    for row in reader:
        time.append( float(row[0]) )
        y1.append( float(row[1]) )

plt.plot(time,y1)

plt.show()

Upvotes: 1

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