s = "text $count$ text"
print s
s.replace("$name$",str(99))
print s
s.replace(str(99),"$name$")
print s

text $count$ text
text $count$ text
text $count$ text

s = "text $count$ text".replace('$count$',str(99))
print s
s = "%s"%(s).replace(str(99),"$count$")
print s
print 'Hello'.replace('l', 'L')

text 99 text
text $count$ text
HeLLo

user@debsrv:/tmp$ cat test.py
s = 'text $count$ text'
print s.replace('$count$','99')

user@debsrv:/tmp$ python test.py
text 99 text

user@debsrv:/tmp$ jython test.py
text 99 text

user@debsrv:/tmp$ python --version
Python 2.6.6
user@debsrv:/tmp$ jython --version
Jython 2.5.1+

user@debsrv:/tmp$ cat test2.py 
s = "text $count$ text"
s =s.replace('$count$',str(99))
print s
s = s.replace(str(99),"$count$")
print s
print 'Hello'.replace('l', 'L')

user@debsrv:/tmp$ python test2.py 
text 99 text
text $count$ text
HeLLo