Why its dont work?

Hello! I am a python beginner. I write a code, with pyowm module (Pyowm on github: https://github.com/csparpa/pyowm), but its for some reason wrong. I has download the pyowm module and I using the terminal for module installation on python 3. My os is Mac OS X Yosemite and the my python version is 3.6.3. I even use Sublime Text 3 as a code editor. What I do wrong? Please help me!
My code:
   
    import pyowm
   
    city = input('Write a city for weather analysis:')
   
    owm = pyowm.OWM('5f28df836a35fc458e6270eb8f01ec86')
    observation = own.weather_at_place(city)
    w = observation.get_weather()
    temperature = w.get_temperature('celsius')['temp']
   
    print("The temperature in" + city + "is: " + str(temperature) + "on celsius")

But python say:

Traceback (most recent call last):
  File "untitled.py", line 3, in <module>
    city = input('Write a city for weather analysis:')
  File "<string>", line 1, in <module>
NameError: name 'London' is not defined
SBSC02PBB8G9402:pythonpractice dchim$ python untitled.py
Write a city for weather analysis: London
Traceback (most recent call last):
  File "untitled.py", line 3, in <module>
    city = input(str('Write a city for weather analysis:'))
  File "<string>", line 1, in <module>
NameError: name 'London' is not defined.


Thanks!!!
untitled.py