Python 2.7以.csv格式导出数据

Question

I have this piece of code that works at gathering data from a serial port connected machine, the data is then reordered. I can successfully print my data at the end : print pigment_data

However I don't get how to export this data to a .csv file.

Is there any straightforward way to do this?

Thank you very much,

Adrien

import serial  # requires pyserial library
import csv

ser  = serial.Serial(0)
data = []

while True:
    name = raw_input("Pigment name [DONE to finish]: ")
    if name == "DONE":
        break

    pigment_data = []
    first = True
    main_spect = []

    while True:
        line = ser.readline()
        if first:
            print "  Data incoming..."
            first = False
        split = line.split()
        if 10 <= len(split):
            try:
                wavelength = int(split[0])
                measurements = [float(split[i]) for i in [2,4,6,8,10]]
                pigment_data.append({"wavelength": wavelength,
                                     "measurements": measurements})
                main_spect.append(measurements[2])
            except ValueError:
                pass    # handles the table heading
        if line[:3] == "110":
            break
    data.append({"name": name,
                 "data": pigment_data})
    print "  Data gathered."
    print pigment_data

    # here's the problem:
    with open('spectral_data.csv', 'wb') as f:
        writer = csv.writer(f)
        writer.writerows(pigment_data)

Answer 1

You gathered a list of dictionaries, use csv.DictWriter() here instead to make this easier:

with open('spectral_data.csv', 'ab') as f:
    writer = csv.DictWriter(f, ('name', 'data'))
    writer.writerow(data[-1])

This opens the file in append-mode as well, since you are opening the file once every loop. I used data[-1] here because that's the last entry you added in the loop.

You probably want to move the creation of the writer object out of your loop:

with open('spectral_data.csv', 'wb') as f:
    writer = csv.DictWriter(f, ('name', 'data'))

    while True:
        name = raw_input("Pigment name [DONE to finish]: ")
        # ....

        print pigment_data

        writer.writerow(data[-1])

which writes the newest entry you gathered to the CSV file as you gather it.

Last but not least, you can also write the whole data list in one go after the outer while True: is done:

data = []

while True:
    name = raw_input("Pigment name [DONE to finish]: ")
    # ....

with open('spectral_data.csv', 'ab') as f:
    writer = csv.DictWriter(f, ('name', 'data'))
    writer.writerows(data)

Answer 2

from csv.writer 's help:

writer(...)
    csv_writer = csv.writer(fileobj [, dialect='excel']
                                [optional keyword args])
        for row in sequence:
            csv_writer.writerow(row)

        [or]

        csv_writer = csv.writer(fileobj [, dialect='excel']
                                [optional keyword args])
        csv_writer.writerows(rows)

    The "fileobj" argument can be any object that supports the file API.

so basically you want:

with open('spectral_data.csv', 'wb') as f:
    writer = csv.writer(f)
    for row in pigment_data:
        writer.writerow(row)