JIYIK CN >

This tutorial will show you various ways to implement a one-line loop in Python for. In Python, a one-line forloop can take many forms; a simple forfor loop can iterate over an iterable object or a sequence. Another can be a simple list comprehension or if ... elsea list comprehension with an for statement.

forA simple one-line loop in Python

A simple one-line forloop is fora loop, which loops over a sequence or an iterable object. So, we can use iterable objects with forloops or range()functions. An iterable object can be a list, array, set or dictionary.

The following code example demonstrates how to implement a one-line forloop to iterate over a Python iterable object.

myset = {"a", "b", "c", "d", "e", "f", "g"}
mydict = {"a": 1, "b": 2, "c": 3, "d": 4, "e": 5, "f": 6, "g": 7}

for x in myset:
    print(x)

for key, val in mydict.items():
    print(key, val)

range(start, stop, step)The function returns a sequence that startstarts at value and stopends at value with a step size equal to step.

The following sample code demonstrates how to use range()the function to implement a one-line loop in Python for.

for x in range(1, 99):
    # do something

forList comprehensions in Python using a single-line loop

List comprehension is a syntactic method of creating a new list from an existing list in many programming languages, including Python. We can apply any operation to each element of a list and create a new list using simple list comprehension.

The following sample code demonstrates how to implement list comprehension in Python using a single-line forloop. The following code creates a new list by taking the square of each element in the existing list.

mylist = [6, 2, 8, 3, 1]

newlist = [x ** 2 for x in mylist]
print(newlist)

Output:

[36, 4, 64, 9, 1]

Using the single-line loop for list comprehensions in Python using if ... elsethefor

List comprehensions with if ... elsethe statement are used to apply an operation on some specific elements of an existing list to create a new list, or to filter elements from an existing list to create a new list.

The following sample code demonstrates how to use forthe loop to implement list comprehension in Python using ifthe and if...elsestatements.

The example code below adds the element to a new list if it is an odd number and discards it if it is an even number.

mylist = [1, 4, 5, 8, 9, 11, 13, 12]

newlist = [x for x in mylist if x % 2 == 1]
print(newlist)

Output:

[1, 5, 9, 11, 13]

The following example code uses a single if ... elseline of list comprehension to add the odd elements as 1, convert the odd elements to even numbers, and add the even elements to the list without doing anything on them, as a result, we get a new list of even numbers.

mylist = [1, 4, 5, 8, 9, 11, 13, 12]

newlist = [x + 1 if x % 2 == 1 else x for x in mylist]
print(newlist)

Output:

[2, 4, 6, 8, 10, 12, 14, 12]