[Tut] For Loop with Two Variables (for i j in python)

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For Loop with Two Variables (for i j in python)

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for i j in python

The Python expression

Code:

for i, j in XXX

allows you to iterate over an iterable

Code:

XXX

of pairs of values. For example, to iterate over a list of tuples, this expression captures both tuple values in the loop variables

Code:

i

and

Code:

j

at once in each iteration.

Here’s an example:

Code:

for i, j in [('Alice', 18), ('Bob', 22)]: print(i, 'is', j, 'years old')

Output:

Code:

Alice is 18 years old Bob is 22 years old

Notice how the first loop iteration captures

Code:

i='Alice'

and

Code:

j=18

, whereas the second loop iteration captures

Code:

i='Bob'

and

Code:

j=22

.

for i j in enumerate python

The Python expression

Code:

for i, j in enumerate(iterable)

allows you to loop over an iterable using variable

Code:

i

as a counter (0, 1, 2, …) and variable

Code:

j

to capture the iterable elements.

Here’s an example where we assign the counter values

Code:

i=0,1,2

to the three elements in

Code:

lst

:

Code:

lst = ['Alice', 'Bob', 'Carl'] for i, j in enumerate(lst): print(i, j)

Output:

Code:

0 Alice 1 Bob 2 Carl

Notice how the loop iteration capture:

• Code:

  i=0
  and
  Code:

  j='Alice'
  ,
  
  
• Code:

  i=1
  and
  Code:

  j='Bob'
  , and
  
  
• Code:

  i=2
  and
  Code:

  j='Carl'
  .
  

Learn More: The

Code:

enumerate()

function in Python.



for i j in zip python

The Python expression

Code:

for i, j in zip(iter_1, iter_2)

allows you to align the values of two iterables

Code:

iter_1

and

Code:

iter_2

in an ordered manner and iterate over the pairs of elements. We capture the two elements at the same positions in variables

Code:

i

and

Code:

j

.

Here’s an example that zips together the two lists

Code:

[1,2,3]

and

Code:

[9,8,7,6,5]

.

Code:

for i, j in zip([1,2,3], [9,8,7,6,5]): print(i, j)

Output:

Code:

1 9 2 8 3 7

Learn More: The

Code:

zip()

function in Python.



for i j in list python

The Python expression

Code:

for i, j in list

allows you to iterate over a given list of pairs of elements (list of tuples or list of lists). In each iteration, this expression captures both pairs of elements at once in the loop variables

Code:

i

and

Code:

j

.

Here’s an example:

Code:

for i, j in [(1,9), (2,8), (3,7)]: print(i, j)

Output:

Code:

1 9 2 8 3 7

for i j k python

The Python expression

Code:

for i, j, k in iterable

allows you to iterate over a given list of triplets of elements (list of tuples or list of lists). In each iteration, this expression captures all three elements at once in the loop variables

Code:

i

and

Code:

j

.

Here’s an example:

Code:

for i, j, k in [(1,2,3), (4,5,6), (7,8,9)]: print(i, j, k)

Output:

Code:

1 2 3 4 5 6 7 8 9

for i j in a b python

Given two lists

Code:

a

and

Code:

b

, you can iterate over both lists at once by using the expression

Code:

for i,j in zip(a,b)

.

Given one list

Code:

['a', 'b']

, you can use the expression

Code:

for i,j in enumerate(['a', 'b'])

to iterate over the pairs of (identifier, list element) tuples.

Summary

The Python

Code:

for

loop is a powerful method to iterate over multiple iterables at once, usually with the help of the

Code:

zip()

or

Code:

enumerate()

functions.

Code:

for i, j in zip(range(10), range(10)): # (0,0), (1,1), ..., (9,9)

If a list element is an iterable by itself, you can capture all iterable elements using a comma-separated list when defining the loop variables.

Code:

for i,j,k in [(1,2,3), (4,5,6)]: # Do Something