Say hello!

Write a function to greet a person. Function will take name as input and greet the person by saying hello.
Return null/nil/None if input is empty string or null/nil/None.

Example: 

```python
greet("Niks") --> "hello Niks!"
greet("")    --> None # Return None if input is empty string
greet(None)  --> None # Return None if input is None
```

Difficulty: introductory

Starter code:

def greet(name):
	

Solutions:
def greet(name):
    return f"hello {name}!" if name else None

def greet(name):
    if name:
        return f"hello {name}!"

def greet(s):
    if s: return f"hello {s}!"

def greet(name=None):
    return "hello {}!".format(name) if name else None


def greet(n):
    if n:
        return f"hello {n}!"

def greet(name):
    if name==None:
        return None
    if name=='':
        return None
    n=len(name)    
    if n>=1:
        return "hello"+' '+name+'!'

def greet(name):
    if name == None:
        return None
    
    if len(name) > 0:
        return "hello " + name + "!"
    else:
        return None

def greet(name):
    # your code here
    if name == "":
        return None
    elif isinstance(name,str):
        return "hello "+ name + "!"
    else:
        return None

def greet(name):
    if name is "" or name is None: 
        return None
    else:
        return f"hello {name}!"  

def greet(name):
    if name in ['', None]:
        return None
    return f"hello {name}!"