python使用csv模塊讀寫csv文件

原文：https://www.getdatajoy.com/examples/python-data-analysis/read-and-write-a-csv-file-with-the-csv-module

Example that shows how to read and write a Comma Separated Value (cvs) filewith thecsv python module.

This example reads a file named smallsample.cvs whose column labels arefirst_name,last_name, company_name, address, city,county,postal, phone1, phone2,email, web. First the csv module isimported.

import csv

Now a new dialect called mydialect is created, the default dialect is excel

csv.register_dialect(
    'mydialect',
    delimiter = ',',
    quotechar = '"',
    doublequote = True,
    skipinitialspace = True,
    lineterminator = '\r\n',
    quoting = csv.QUOTE_MINIMAL)

Now we open and print the file and create an iterable object with thereader() routine, then we use afor loop to print the data.The with statement automatically closes the file when finished.

print('\n Output from an iterable object created from the csv file')
with open('smallsample.csv', 'rb') as mycsvfile:
    thedata = csv.reader(mycsvfile, dialect='mydialect')
    for row in thedata:
        print(row[0]+"\t \t"+row[1]+"\t \t"+row[4])

Output:

Output from an iterable object created from the csv file
first_name      last_name               city
Aleshia         Tomkiewicz              St. Stephens Ward
Evan            Zigomalas               Abbey Ward
France          Andrade                 East Southbourne and Tuckton W
Ulysses         Mcwalters               Hawerby cum Beesby
Tyisha          Veness                  Greets Green and Lyng Ward
Eric            Rampy                   Desborough
Marg            Grasmick                Bargate Ward
Laquita         Hisaw                   Chirton Ward
Lura            Manzella                Staple Hill Ward

---

Dictionary From CSV File

This example opens the file and makes a dictionary whose keys are theentries in the first row of the data file. TheDictReader() routineaccomplished this.The with statement automatically closes the file when finished

print("\n Now the output from a dictionary created from the csv file")
with open('smallsample.csv', 'rb') as mycsvfile:
    dictofdata = csv.DictReader(mycsvfile, dialect='mydialect')
    for row in dictofdata:
        print(row['first_name']+"\t "+row['phone1']+"\t "+row['city'])

Output:

Now the output from a dictionary created from the csv file
Aleshia  01835-703597    St. Stephens Ward
Evan     01937-864715    Abbey Ward
France   01347-368222    East Southbourne and Tuckton W
Ulysses  01912-771311    Hawerby cum Beesby
Tyisha   01547-429341    Greets Green and Lyng Ward
Eric     01969-886290    Desborough
Marg     01865-582516    Bargate Ward
Laquita  01746-394243    Chirton Ward
Lura     01907-538509    Staple Hill Ward

---

Write An Array To A CSV File

Now an example about writing, a file called mydata.csv with the contents ofthe arrayarrayofdata will be created. The file is created by thewriter() routine, then each row is written withwriterow().The with statement automatically closes the file when finished

arrayofdata=[[1,2,4,5,'something','spam',2.334],
             [3,1,6,3,'anything','spam',0]]
             
with open('mydata.csv', 'w') as mycsvfile:
    thedatawriter = csv.writer(mycsvfile, dialect='mydialect')
    for row in arrayofdata:
        thedatawriter.writerow(row)