appending a single string to each element of a list in python

Question

I'm trying to read a text file containing a list of user IDs and convert those IDs into email addresses by appending the @wherever.com ending to the IDs. Then I want to write those email addresses to a new file separated by commas.

textFile = open(“userID.txt”, “r”)
identList = textFile.read().split(“, “)
print identList
textFile.close()

emailString = “@wherever.com, ”
newList = [x +  emailString for x in identList]

writeFile = open(“userEmail.txt”, “w”)
writeFile.writelines(newList)
writeFile.close()

I'm using python 3.x for Mac. This isn't working at all. I'm not sure if it is reading the initial file at all. It is certainly not writing to the new file. Can someone suggest where the program is failing to work?

Is this your real code? Because I don't think those fancy quotes are going to work. — Two-Bit Alchemist
– Two-Bit Alchemist, Commented Sep 2, 2015 at 17:48

Martin Evans · Accepted Answer · 2015-09-03 14:18:57Z

2

Something like the following should work:

with open('userID.txt', 'r') as f_input, open('emails.txt', 'w') as f_output:
    emails = ["{}@wherever.com".format(line.strip()) for line in f_input]
    f_output.write(", ".join(emails))

So if you had a userID.txt file containing the following names, with one name per line:

fred
wilma

You would get a one line output file as follows:

[email protected], [email protected]

edited Sep 3, 2015 at 14:18

answered Sep 2, 2015 at 16:34

Martin Evans

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7 Comments

D. Johnson Over a year ago

This doesn't quite work. The output is: fred [email protected] The only the last entry has the email component appended and there are no commas separating entries.

Martin Evans Over a year ago

It assumes your input file is a list of names, one per line. It could be changed to read a single line.

D. Johnson Over a year ago

The input file actually is a list of names, one per line. The output is a list of names, one per line as well, but only the last name on the last line has the appended @wherever.com.

Martin Evans Over a year ago

Are you sure the code is the same? I had made a small change shortly after posting.

D. Johnson Over a year ago

It is exactly as it appears in your post above.

|

primero · Accepted Answer · 2015-09-02 17:47:39Z

0

You could do it like this, also using context managers for reading and writing, because then you don't need to worry about closing the file:

identList = []
with open('userID.txt', 'r') as f:
    identList = f.readlines().rstrip().split(',')

outString = ','.join([ '{0}@wherever.com'.format(x) for x in identList ])

with open('userEmail.txt', 'w') as f:
   f.write(outString)

The conversion to string was done with join, which joins in this case the list elements formed in the comprehension with commas between them.

edited Sep 2, 2015 at 17:47

answered Sep 2, 2015 at 16:34

primero

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