在Python中使用变量的问题

Question

I am a beginner in Python and I know this question is pretty basic but I can't seem to find the solution from Googling.

I am writing a simple scraping script in Python and I am using BeautifulSoup for parsing. I am just stuck in using a variable to set the filename of my CSV write functions. say I have a variable called "category", how can I set that as the name of the CSV file?

category = "student"

with open('%category.csv', 'a') as csv_file:  
   writer = csv.writer(csv_file)
   writer.writerow([cname, caddress, ccontact])

Answer 1

Try this:

with open(category + '.csv', 'a') as csv_file:  

You do not substitute the variable like that. Read a basic book.

Answer 2

Try this instead:

with open('%s.csv' % category, 'a') as csv_file:  

See this informative article for more on string formatting in Python.

Answer 3

Use format() like this:

with open('{}.csv'.format(category), 'a') as csv_file:

Output:

>>> category = 'my_file'
>>> '{}.csv'.format(category)
'my_file.csv'

Answer 4

This task can be achieved by many ways and few of which are listed below :

1. String Concatenation .

    category = "student" with open(category + '.csv', 'a') as csv_file: 

2. String Formatting

     with open('%s.csv' % category, 'a') as csv_file: 

3. Using format() function

    with open('{}.csv'.format(category), 'a') as csv_file: 

I hope these all will work fine for you.

Best One is :-

category = "student.csv" 
with open(category, 'a') as csv_file:

The last one is simplest one , to change the name of file just change the value of variable.