python使用csv模块读写csv文件

╰半橙微兮° 2022-09-21 14:25 323阅读 0赞

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 the**csv** python module.

This example reads a file named *smallsample.cvs* whose column labels are`first_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 the`reader()` routine, then we use a`for` 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. The`DictReader()` 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 array`arrayofdata` will be created. The file is created by the`writer()` routine, then each row is written with`writerow()`.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)