I have a list in Python, and I want to check if any elements are negative. Is there a simple function or syntax I can use to apply the "is negative" check to all the elements, and see if any of them is negative? I looked through the documentation and couldn't find anything similar. The best I could come up with was:
if (True in [t < 0 for t in x]):
# do something
I find this rather inelegant. Is there a better way to do this in Python?
Existing answers here use the built-in function any
to do the iteration. See How do Python's any and all functions work? for an explanation of any
and its counterpart, all
.
If the condition you want to check is "is found in another container", see How to check if one of the following items is in a list? and its counterpart, How to check if all of the following items are in a list?. Using any
and all
will work, but more efficient solutions are possible.
Python all() Function The all() function returns True if all items in an iterable are true, otherwise it returns False. If the iterable object is empty, the all() function also returns True.
Besides the Find and Replace function, you can use a formula to check if a value is in a list. Select a blank cell, here is C2, and type this formula =IF(ISNUMBER(MATCH(B2,A:A,0)),1,0) into it, and press Enter key to get the result, and if it displays 1, indicates the value is in the list, and if 0, that is not exist.
How to check if a variable exists in Python. To check if a local variable exists in Python, use in operator and check inside the locals() dictionary. To check if a global variable exists in Python, use in operator and check inside the globals() dict. To check if an object has an attribute, use the hasattr() function.
any():
if any(t < 0 for t in x):
# do something
Also, if you're going to use "True in ...", make it a generator expression so it doesn't take O(n) memory:
if True in (t < 0 for t in x):
Use any()
.
if any(t < 0 for t in x):
# do something
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