CODEWITHSUNDEEP
pythonlistif-statement
ThorSummoner
ThorSummoner

Reputation: 18109

python test if substring in all item in a list

I want to do like all all() like comparison to test if my substring is in every element in the list.

Some dummy data:

let my_list = ['~/.tmp/myproject/filea', '~/.tmp/myproject/fileb']

I want to test if .tmp/myproject/ is in every item in this list.

Upvotes: 1

Views: 94

Answers (2)

Padraic Cunningham
Padraic Cunningham

Reputation: 180441

Some timings show exactly why you should use a generator expression:

In [25]:  l = ["foobar" for _ in range(100000)]

In [26]:  l = ["foobar" for _ in range(100000)]

In [27]: l =  ["doh"] + l

In [28]: timeit all("foo" in s for s in l)
1000000 loops, best of 3: 541 ns per loop

In [29]: timeit all(["foo" in s for s in l])
100 loops, best of 3: 6.49 ms per loop

There are some nice example of how to use generators and their advantages here wiki.python.org/moin/Generators

I think a good rule of thumb is if you only plan on using the set of elements generated once or the data is too large to fit in memory use a generator expression. If you want to use the elements again and the size is practical then store them in a list.

Upvotes: 2

ThorSummoner
ThorSummoner

Reputation: 18109

all(['mysubstring' in item for item in my_list])

List comprehension is perhapse the best way to do this kind of check, and best of all you can still use all!

Python 2.7.6 (default, Mar 22 2014, 22:59:56)
Type "help", "copyright", "credits" or "license" for more information.
>>> my_list = ['~/.tmp/myproject/filea', '~/.tmp/myproject/fileb']
>>> my_list
['~/.tmp/myproject/filea', '~/.tmp/myproject/fileb']
>>> [item for item in my_list]
['~/.tmp/myproject/filea', '~/.tmp/myproject/fileb']
>>> ['/.tmp/myproject/' in item for item in my_list]
[True, True]
>>> all(['/.tmp/myproject/' in item for item in my_list])
True

Upvotes: 3

Related Questions