Search in an object list attribute in Python

Question

How to search in a list of objects attribute ? Suppose i want the fname of all object and also the age > 30 or some match found

#!usr/bin/python
import sys
import pickle

class People:
    def __init__(self, fname=None, lname=None, age=None, gender=None):
        self.fname = fname
        self.lname = lname
        self.age = age
        self.gender = gender

    def display(self):

        #fp = open("abc","w")
        #fp.write("F.Name: "+ppl.fname+ "\nLName: "+ ppl.lname + "\nAge: "+     str(ppl.age)+ "\nGender: "+ ppl.gender) 




ppl = [People("Bean", "Sparrow", 22, "M"), People("Adam", "Sandler", 32, "M"),     People("Jack", "Marro", 28, "M")]

fp = open("abc","w")
for person in ppl:
    fp.write("F.Name: "+person.fname+ "\nLName: "+ person.lname+ "\nAge: "+     str(person.age)+ "\nGender: "+ person.gender+"\n\n")
fp.close()

Answer 1

In Python there's a thing called list comprehensions . And list comprehensions are your friend.

Get all ppl.fname :

all_fnames = [person.fname for person in ppl]

Get all persons with ppl.age greater than 30:

all_greater_than_thirty = [person for person in ppl if person.age > 30]

And so on.

EDIT Since a list comprehension returns a list, you would just use that in place of whatever list you originally had, for example to write to file:

with open("abc", "w") as fp:
    for person in [p for p in ppl if p.age > 30]:
        fp.write(...) # Fill it in with whatever you want to write

Or even better, but more advanced, you would create a method for your People class that would return a string formatted to write to file, something like People.to_string() , then you could do this:

with open("abc", "w") as fp:
    fp.writelines("%s\n" % person.to_string() for person in ppl if person.age > 30)

The advantage is efficiency. Plus it looks nicer.

Answer 2

You can get the names of people older than 30 using list comprehension:

names_list = [person.name for person in ppl if person.age > 30]

and do whatever you want to do with them :)

Answer 3

Is this what you're looking for:

for person in [p for p in ppl if (p.fname is "name" and p.age < 30)]:
    # Do whatever you want with it...