I have a list 'a'
a= [(1,2),(1,4),(3,5),(5,7)]I need to find all the tuples for a particular number. say for 1 it will be
result = [(1,2),(1,4)]How do I do that?
10 Answers
If you just want the first number to match you can do it like this:
[item for item in a if item[0] == 1]If you are just searching for tuples with 1 in them:
[item for item in a if 1 in item]There is actually a clever way to do this that is useful for any list of tuples where the size of each tuple is 2: you can convert your list into a single dictionary.
For example,
test = [("hi", 1), ("there", 2)]
test = dict(test)
print test["hi"] # prints 1Read up on List Comprehensions
[ (x,y) for x, y in a if x == 1 ]Also read up up generator functions and the yield statement.
def filter_value( someList, value ): for x, y in someList: if x == value : yield x,y
result= list( filter_value( a, 1 ) )[tup for tup in a if tup[0] == 1]for item in a: if 1 in item: print itemThe filter function can also provide an interesting solution:
result = list(filter(lambda x: x.count(1) > 0, a))which searches the tuples in the list a for any occurrences of 1. If the search is limited to the first element, the solution can be modified into:
result = list(filter(lambda x: x[0] == 1, a))Using filter function:
>>> def get_values(iterables, key_to_find):
return list(filter(lambda x:key_to_find in x, iterables)) >>> a = [(1,2),(1,4),(3,5),(5,7)] >>> get_values(a, 1) >>> [(1, 2), (1, 4)]
>>> [i for i in a if 1 in i][(1, 2), (1, 4)]
1Or takewhile, ( addition to this, example of more values is shown ):
>>> a= [(1,2),(1,4),(3,5),(5,7),(0,2)]
>>> import itertools
>>> list(itertools.takewhile(lambda x: x[0]==1,a))
[(1, 2), (1, 4)]
>>> if unsorted, like:
>>> a= [(1,2),(3,5),(1,4),(5,7)]
>>> import itertools
>>> list(itertools.takewhile(lambda x: x[0]==1,sorted(a,key=lambda x: x[0]==1)))
[(1, 2), (1, 4)]
>>> if you want to search tuple for any number which is present in tuple then you can use
a= [(1,2),(1,4),(3,5),(5,7)]
i=1
result=[]
for j in a: if i in j: result.append(j)
print(result)You can also use if i==j[0] or i==j[index] if you want to search a number in particular index
