Python: How to check if string is in list?

How to check if a string is in a list?
How to check if a string is an element of a list in Python? There are different ways to check if a string is an element of a list.


in operator
list.count() method
list.index() method


To check if a string is part of any element in the list, use the any() function and list comprehensions.


# check if string is part of any element
myList = ['myHouse', 'myCar', 'myBoat']
any('House' in str for str in myList)


House is present in the list, True is returned.

True

Option 1: in operator
To check if a string is in a list, use the in operator on the list.


# check if string is in a list using in operator
myList = ['a', 'b', 'c']
if 'a' in myList:
   True


The letter a is in myList, True is returned.

True

Option 2: list.count() method
The list.count() method returns how often a string is in a list. If the returned number is over 0, we know the string is at least once in the list.


# check if string is in a list using list.count() method
myList = ['a', 'b', 'c']
if myList.count('a') > 0:
  True


The letter a is once in myList. The count is higher than 0, therefore True is returned.

True

Option 3: list.index() method
The third option is similar to the second option. The difference is that we need to take care of exception handling, because if the index is not found an ValueError exception is raised.

ValueError: 'z' is not in list

To take care of it wrap the code into a try/except block.


# check if string is in a list using list.index() method
myList = ['a', 'b', 'c']
try:
   if myList.index('a'):
      pass
except:
   # ValueError exception means string is not in list
   False
else:
   # No exception means string is in list
   True


The letter a is in the list of letters. Because no exception is raised, the else block is executed and True is returned.

True