Iterate through list and check if I am at end of list

user_13286790 0
Viewed 4150

I have a list of strings:

animals = ["cat meow ", "dog bark"]

And I want to check if each string contains the word "cow" which obviously does not exist in my above list. I am trying to write an if else statement that checks if I am at the end of the list and if cow is not found print "not found ".

The code below prints not found for every element that does not contain the string but I want to print "not found" just once when I iterate my whole list at the end of it but I do not know the correct syntax. 

animals = ['dog bark' , 'cat meow ']
for pet in animals:
  if 'cow' in pet:
    print('found')
  else:
    print('not  found')
for-loop list python
5 Answers

This seems like a good use case for Python's any() function, which returns True if any of the items in an iterable are true.

animals = ['dog bark' , 'cat meow ']
has_cow = any('cow' in a for a in animals)
print('found' if has_cow else 'not found')

But, if you're super eager to use a for loop, you could either use a flag variable to track whether you found the item inside the loop or take advantage of Python's truly strange for-else construct (the else clause executes if the loop was not broken out of). In over a dozen years of Python programming, I have never used for-else, so it's really just a language curiosity, and I strongly discourage it. But it does work for this specific problem!

for a in animals:
    if 'cow' in a:
        print('found')
        break
else:                      # WTF!?!  Don't do this, folks.
    print('not found')
Monty_Hindman_558570 
animals = ['dog bark' , 'cat meow ']

print('found' if any('cow' in pet for pet in animals) else 'not found')

It works with variables too;

result = 'found' if any('cow' in pet for pet in animals) else 'not found'
user_136560450

The flag comes in handy at such situations 

flag = False
animals = ['dog bark' , 'cat meow']
for pet in animals:
  if 'cow' in pet:
      print("Found")
      flag = True

if flag == False:
    print("Not found")

It will print "Not Found"

For animals = ['dog bark', 'cat meow', "cow moo"], it will print "Found".

user_102400850

Most programming languages allow the use of else statements with if conditional statements only. However in Python, the else statement can also be used with for loops, of which most of us are unfamiliar. Generally the for/else is used to run a loop when we search for an item. Eg:

lis=[1,2,3]
for i in lis:
    if i==1:
        print("1 found in list.")
        break
else:
    print("1 is not in list.")

This code will print: 1 found in list. When the loop runs, i takes values in the list, and the if statement will check the provided conditions, if the condition is true, the print statement will be executed. After that, the break statement is excecuted which breaks the flow of control in the code. Break statement in Python is used to bring control out of the loop, when some condition is triggered.

Thus the code in the question can correctly be written as: 

animals=["dog bark","cat meow"]
for pet in animals:
    if 'cow' in pet:
        print("Found")
        break'
else:
    print("not found")

This will print the desired result!

Hope it helps!

user_137379900

You can achieve that the not found print will be printed once by 

animals = ['dog bark' , 'cat meow ']
for i, pet in enumerate(animals):
  if 'cow' in pet:
    print('found')
    break
  elif i+1 == len(animals):
    print('not  found')

Or in one line

print("found" if [i for i in animals if "cow" in i] else "not  found")

This code will print found and exit the loop if there is a cow in one of the else it will check in the last item of it the cow not in the item then it will print 'not found'.

user_131012390
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