Prepend each line in a string python
<p>I have a variable that holds the below value:</p>

<pre><code>From: test@example.com
To: user1@us.oracle.com
Date: Thu Sep 29 04:25:45 2016
Subject: IMAP Append Client FNBJL
MIME-version: 1.0
Content-type: text/plain; charset=UTF-8; format=flowed

  hocks burdock steelworks propellants resource querying sitings biscuits lectureship
  linearly crimea ghosting inelegant contingency resting fracas margate radiographic
  befoul waterline stopover two everlastingly highranking doctrine unsmilingly massproducing
 teacups litanies malachite pardon rarer glides nonbelievers humorously clonal tribunes
micrometer paralysing splenetic constitutionalists wavings thoughtfulness herbicide
rerolled ore overflows illicitly aerodynamics ably splittable ditching rouged bulldozer
replayed statistic reconfigured adventurers passionate rewarded decides oxygenated
</code></pre>

<p>Every line in the above string needs to be prepended with <code>X:</code> as shown below</p>

<pre><code>X: From: test@example.com
X: To: user1@us.oracle.com
X: Date: Thu Sep 29 04:25:45 2016
X: Subject: SSSSSSSSS FNBJL
X: MIME-version: 1.0
X: Content-type: text/plain
X: 
X:   hocks burdock steelworks propellants resource querying sitings biscuits lectureship
X:  linearly crimea ghosting inelegant contingency resting fracas margate radiographic
X:  befoul waterline stopover two everlastingly highranking doctrine unsmilingly massproducing
X:  teacups litanies malachite pardon rarer glides nonbelievers humorously clonal tribunes
X:  micrometer paralysing splenetic constitutionalists wavings thoughtfulness herbicide
X:  rerolled ore overflows illicitly aerodynamics ably splittable ditching rouged bulldozer
X:  replayed statistic reconfigured adventurers passionate rewarded decides oxygenated
</code></pre>

<p>I was thinking of splitting the above string on <code>\n</code> and prepending each line with <code>X:</code></p>

<p>Is there a better approach for this?</p>

<p>There are tons of ways to achieve what you want, here's few ones:</p>

<pre><code>import re

log = """From: test@example.com
To: user1@us.oracle.com
Date: Thu Sep 29 04:25:45 2016
Subject: IMAP Append Client FNBJL
MIME-version: 1.0
Content-type: text/plain; charset=UTF-8; format=flowed

  hocks burdock steelworks propellants resource querying sitings biscuits lectureship
  linearly crimea ghosting inelegant contingency resting fracas margate radiographic
  befoul waterline stopover two everlastingly highranking doctrine unsmilingly massproducing
 teacups litanies malachite pardon rarer glides nonbelievers humorously clonal tribunes
micrometer paralysing splenetic constitutionalists wavings thoughtfulness herbicide
rerolled ore overflows illicitly aerodynamics ably splittable ditching rouged bulldozer
replayed statistic reconfigured adventurers passionate rewarded decides oxygenated"""


def f1(text):
    return "X: " + text.replace("\n", "\nX: ")


def f2(text):
    return "X: " + re.sub('\n', '\nX: ', text)


def f3(text):
    return "\n".join(["X: {0}".format(l) for l in text.split("\n")])

if __name__ == "__main__":
    print(log)

    for f in [f1, f2, f3]:
        print('-' * 80)
        print(f(log))
</code></pre>

python python-2.7