Hi @charry, there are at least two ways.

1. Create new attribute, remove old attribute.

def renameExample(feature):
    v = feature.getAttribute('oldName')
    feature.setAttribute('newName', v)
    feature.removeAttribute('oldName')

2. Rename attribute using the FME function @RenameAttributes

def renameExample2(feature):
    feature.performFunction('@RenameAttributes(newName,oldName)')

See here to learn more about FME Functions: FME Factory and Function Documentation

def renameExample(feature):
    v = feature.getAttribute('oldName')
    feature.setAttribute('newName', v)
    feature.removeAttribute('oldName')

def renameExample2(feature):
    feature.performFunction('@RenameAttributes(newName,oldName)')

ERROR:

Python Exception <IndentationError>: expected an indented block (<string>, line 10)

Error executing string `import<space>fme<lf>import<space>fmeobjects<lf>#<space>Template<space>Function<space>interface:<lf>#<space>When<space>using<space>this<space>function<comma><space>make<space>sure<space>its<space>name<space>is<space>set<space>as<space>the<space>value<space>of<lf>#<space>the<space><apos>Class<space>or<space>Function<space>to<space>Process<space>Features<apos><space>transformer<space>parameter<space><lf>def<space>processFeature<openparen>feature<closeparen>:<lf><space><space><space><space>a=feature.getAttributeNullMissingAndType<openparen><apos>BZ<apos><closeparen><lf><space><space><space><space>if<space>a<openbracket>1<closebracket>==true:<lf><space><space><space><space>feature.performFunction<openparen><apos><at>RenameAttributes<openparen><apos>KD<apos><comma><apos>BZ<apos><closeparen><apos><closeparen><lf>#<space><space><space><space><space><space><space><space>v<space>=<space>feature.getAttribute<openparen><apos>BZ<apos><closeparen><lf>#<space><space><space><space><space><space><space><space>feature.setAttribute<openparen><apos><u5907><u6ce8><apos><comma><space>v<closeparen><lf>#<space><space><space><space><space><space><space><space>feature.removeAttribute<openparen><apos>BZ<apos><closeparen><lf><space><space><space><space><space><space><space>#<space>feature.setAttribute<openparen><apos><u5907><u6ce8><apos><comma>feature.getAttribute<openparen>feature.getAttribute<openparen><apos>BZ<apos><closeparen><closeparen><closeparen><space><lf><space><space><space><lf><lf>'

Factory proxy not initialized

PythonCaller (PythonFactory): PythonFactory failed to process feature

A fatal error has occurred. Check the logfile above for details

def renameExample(feature):
    v = feature.getAttribute('oldName')
    feature.setAttribute('newName', v)
    feature.removeAttribute('oldName')

def renameExample2(feature):
    feature.performFunction('@RenameAttributes(newName,oldName)')

why I Can't execute successfully

def renameExample(feature):
    v = feature.getAttribute('oldName')
    feature.setAttribute('newName', v)
    feature.removeAttribute('oldName')

def renameExample2(feature):
    feature.performFunction('@RenameAttributes(newName,oldName)')

firstly check if you have set the Class or Function to Process Features parameter appropriately.

First time use PythonCaller, can you provide some detailed operations?thanks

def renameExample(feature):
    v = feature.getAttribute('oldName')
    feature.setAttribute('newName', v)
    feature.removeAttribute('oldName')

def renameExample2(feature):
    feature.performFunction('@RenameAttributes(newName,oldName)')

Then, correct indentations.

https://docs.safe.com/fme/html/FME_FactFunc/index.html function usage depend performFunction ?

No, the @RenameAttributes function is an FME function (not Python), and the document you link describes FME functions.

def renameExample(feature):
    v = feature.getAttribute('oldName')
    feature.setAttribute('newName', v)
    feature.removeAttribute('oldName')

def renameExample2(feature):
    feature.performFunction('@RenameAttributes(newName,oldName)')

There are excellent tutorials on Python and FME basics, I'd recommend you to start learning from here.

https://knowledge.safe.com/articles/706/python-and-fme-basics.html 

https://knowledge.safe.com/articles/60319/pythoncaller-transformer.html 

def renameExample(feature):
    v = feature.getAttribute('oldName')
    feature.setAttribute('newName', v)
    feature.removeAttribute('oldName')

def renameExample2(feature):
    feature.performFunction('@RenameAttributes(newName,oldName)')

Alternatively you can use the AttributeManager transformer or the AttributeRenamer transformer, if you just need to rename attributes.

Of course it's good to learn Python, but it would take time.