Strings

In the followin PERL code, ‘$x’ is a string -

$x=”My name is Alice”;
print $x,”\n”;

The equivalent Python code is shown below -

x=’My name is Alice’
print x

Substring

The following program prints ‘name’.

$x=”My name is Alice”;
$y=substr($x,3,4);

print $y,”\n”;

The equivalent Python code is shown below -

x=”My name is Alice”
y=x[3:7]
print y

https://docs.python.org/2/library/string.html

Python String is a List

Internally, Python represents each string as an immutable list. Therefore, many list-related commands and functions can be used for strings. Here is an example.

line=”Welcome to the class”

print line[10]
print line[1:9]
print line[::-1]

The first print command prints a single character from the list ‘line’, the second
command prints a substring, and the third one reverses the string.

Functions - upper(), lower()

line=”A to Z”
print line.upper()
print line.lower()

Function - strip()

line=f.readline()
l=line.strip()

print line
print l

Function - find()

mystring=”ATGCAAATGCAT”

print mystring.find(“AAA”)

Function - replace()

mystring=”ATGCAAATGCAT”

new=mystring.replace(“A”,”T”)

print new

The function replace() replaces a substring with a different string.

You can use it to replace or remove letters. For example, the following
code removes all commas from a line.

mystring=”John, Jane, Jill, Juan, Jedi”

new = mystring.replace(“,”,””)

print new

Function - split()

line=”A big fat hen”

x=line.split()
for w in x:
print w

Function - join()

x=["ATGC", "TGGG", "TAAA"]

y=”ATGCTGGGTAAA”

z= ““.join(x)

if(z==y):
print “YES”