rename that strange char

*** rename1.py

import os,sys
nome = sys.argv[1]
final = nome.replace("_", " ")
os.rename(nome, final)

*** rename2.py

#!/usr/bin/env python
# coding:utf-8

import glob
import sys
import os

try:
    parametros = sys.argv[1]
except:
    parametros = "*"

arquivos = glob.glob(parametros)
for nome in arquivos:
    novoNome = nome.replace("_", " ")
    print "%s -> %s" %(nome, novoNome)
    os.rename(nome, novoNome)

print "%d arquivos atingidos." %len(arquivos)

*** rename3.py

import os
import sys  # sys module should be imported
nome = sys.argv[1]
final=""    #final is a null string
for i in nome: #i refers to each char in nome
    if i == "_": # there should be a "==" operator
        ch = " " # a string can be assigned to a new variable
                 # but after that you cannot change that value
                 # of the string via the specific variable
                 # because strings are invariable values
    else:
        ch = i
    final += ch #concatenate ch to final
                #a string can be concatenated to another
                #here you are not changing the string that
                #final originally refers to, but make final refer to a
                #new concatenated string
os.rename(nome, final)