Python offers several different types of arrays for storing data.
Lists are arrays which allow you to store items. These list items can be altered, and are stored in a specific order.
There are several methods you should consider for searching a list in Python– searching for a specific value match, or searching for list items that match a certain condition or set of conditions.
You can also remove items from a list in Python.
Checking if a List Contains an Item Using the ‘in’ Statement
Syntax
The syntax for the ‘in’ statement is as follows:
element in list
It will return TRUE or FALSE as a boolean value depending on the outcome.
Example
Here it is in action:
sports = ["cricket", "tennis", "baseball"]
if "tennis" in sports:
print "tennis is present in the list"
Checking if List Does NOT Contain an Item Using not in
You can also check that a list does not contain a value:
sports = ["cricket", "tennis", "baseball"]
if "basketball" not in sports:
print "basketball is not present in the list"
Checking Using the count() Function
Syntax
The count() function can also be used to check whether an item is present in a list – and it will also tell you how many times it appears:
list.count(element)
It will return an integer count of the number of times the element was encountered.
Example
sports = ["cricket", "tennis", "baseball", "tennis"]
count = sports.count("tennis")
print count # Returns 2
You can then check that the value of count is greater than 0 to see whether the element is present or take another action if the count is higher.
Checking for Items which have a Value Matching Custom Conditions Using any()
Syntax
any(condition for element in list)
It will return TRUE or FALSE as a boolean value depending on the outcome.
Example
sports = ["cricket", "tennis", "baseball"] result = any(len(sport) == 7 for sport in sports) print result # Returns TRUE
The above example checks whether there is an element in the list with 7 letters in it. “cricket” is a match for this, so TRUE is returned.
Conclusion
Common uses for checking whether an item is present in a list may include checking whether a user in your app is a member of a group, whether a certain color of product you have for sale is available, or checking whether a correct answer has been entered for a quiz.
