Read and count

[Mark Lawrence]

Hello and welcome.

Please see my comments below.

On 09/03/2016 21:30, Val Krem via Python-list wrote:
> Hi all,
>
> I am a new learner about python (moving from R to python) and trying  read and count the number of observation  by year for each city.
>
> The data set look like
> city year  x
>
> XC1 2001  10
> XC1   2001  20
> XC1   2002   20
> XC1   2002   10
> XC1 2002   10
>
> Yv2 2001   10
> Yv2 2002   20
> Yv2 2002   20
> Yv2 2002   10
> Yv2 2002   10
>
> out put will be
>
> city
> xc1  2001  2
> xc1   2002  3
> yv1  2001  1
> yv2  2002  3
>
>
> Below is my starting code
> count=0

Seems like you'd want a counter here 
https://docs.python.org/3/library/collections.html#collections.Counter. 
  You'll need to know how to import this so start here 
https://docs.python.org/3/tutorial/modules.html

> fo=open("dat", "r+")

We'd normally use the 'with' keyword here so the file automatically gets 
closed so:-

with open("dat", "r+") as fo:

> str = fo.read();

'str' isn't a good name as it overrides the builtin function of that 
name.  This will read the entire file.  Easiest to loop as in:-

for line in fo.readlines():

Now you'll need a split call to get at your data 
https://docs.python.org/3/library/stdtypes.html#str.split and update 
your counter.  Once this loop is finished use another loop to produce 
your output with print.

> print "Read String is : ", str

The above is for Python 2, it needs parenthesis for Python 3.  I'd 
recommend starting with the latter if that's possible.

>
> fo.close()

Not needed if you use the 'with' keyword as discussed above.

>
> Many thanks
>

No problem as I'm leaving you to put it all together :)

-- 
My fellow Pythonistas, ask not what our language can do for you, ask
what you can do for our language.

Mark Lawrence