How to compare two lists in python?
PythonListPython Problem Overview
How to compare two lists in python?
date = "Thu Sep 16 13:14:15 CDT 2010"
sdate = "Thu Sep 16 14:14:15 CDT 2010"
dateArr = [] dateArr = date.split()
sdateArr = [] sdateArr = sdate.split()
Now I want to compare these two lists. I guess split returns a list. We can do simple comparision in Java like dateArr[i] == sdateArr[i], but how can we do it in Python?
Python Solutions
Solution 1 - Python
You could always do just:
a=[1,2,3]
b=['a','b']
c=[1,2,3,4]
d=[1,2,3]
a==b #returns False
a==c #returns False
a==d #returns True
Solution 2 - Python
a = ['a1','b2','c3']
b = ['a1','b2','c3']
c = ['b2','a1','c3']
# if you care about order
a == b # True
a == c # False
# if you don't care about order AND duplicates
set(a) == set(b) # True
set(a) == set(c) # True
By casting a, b and c as a set, you remove duplicates and order doesn't count. Comparing sets is also much faster and more efficient than comparing lists.
Solution 3 - Python
If you mean lists, try ==:
l1 = [1,2,3]
l2 = [1,2,3,4]
l1 == l2 # False
If you mean array:
l1 = array('l', [1, 2, 3])
l2 = array('d', [1.0, 2.0, 3.0])
l1 == l2 # True
l2 = array('d', [1.0, 2.0, 3.0, 4.0])
l1 == l2 # False
If you want to compare strings (per your comment):
date_string = u'Thu Sep 16 13:14:15 CDT 2010'
date_string2 = u'Thu Sep 16 14:14:15 CDT 2010'
date_string == date_string2 # False
Solution 4 - Python
Given the code you provided in comments, I assume you want to do this:
>>> dateList = "Thu Sep 16 13:14:15 CDT 2010".split()
>>> sdateList = "Thu Sep 16 14:14:15 CDT 2010".split()
>>> dateList == sdataList
false
The split-method of the string returns a list. A list in Python is very different from an array. == in this case does an element-wise comparison of the two lists and returns if all their elements are equal and the number and order of the elements is the same. Read the documentation.
Solution 5 - Python
for i in arr1:
if i in arr2:
return 1
return 0
arr1=[1,2,5]
arr2=[2,4,15]
q=checkarrayequalornot(arr1,arr2)
print(q)
>>0
Solution 6 - Python
From your post I gather that you want to compare dates, not arrays. If this is the case, then use the appropriate object: a datetime object.
Please check the documentation for the datetime module. Dates are a tough cookie. Use reliable algorithms.