Python Revision - Section IX - Another Built-in Functions
Built-in Functions
We’ve already seen some important built-in functions like map, filter and lambda. Now, we’ll see other ones.
Reduce
The function reduce(function, sequence) continually applies the function to the sequence and then returns a sigle value.
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from functools import reduce
lst = [47,11,42,13]
reduce(lambda x,y:x+y, lst)
#prints 113
Lets look at a diagram to get a better understanding of what’s going on here:
As the image shows to us, the reduce() is reducing the sequence, applying the function passed as a parameter until a single final value.
We can use reduce() in a large amount of cases, like: finding the max value of a sequence:
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max_find = lambda a,b: a if (a>b) else b
reduce(max_find, lst)
Zip
zip() makes an iterator that aggregates elements from each of the iterables. It combines two iterators in a sequence of tuples until the shortest iterable is exhausted.
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x = [1,2,3]
y = [4,5,6]
print(list(zip(x,y)))
#prints [(1,4), (2,5), (3,6)]
Enumerate
It allows us to keep a count as we iterate through an object. It’s like labeling a list with an ordered labels.
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lst = ['a', 'b', 'c']
for number, item in enumerate(lst):
print(number)
print(item)
# prints
# 0
# a
# 1
# b
# 2
# c
It’s particularly useful when you have a case where you need to have some sort of tracker:
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for count, item in enumerate(lst):
if count >= 2:
break
else:
print(item)
# prints
# a
# b
We can put a start argument to override the default value of zero:
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enumerate(lst, start=1)
all() and any()
Are built-in functions that allow us to check for boolean matching in an iterable.
all(lst) willl return True if all elements of lst are True.
any(lst) willl return True if any elements of lst is True.
I hope it will be helpful to you and if there’s any questions or something else, please, feel free to contact me.
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