Skip over a value in the range function in python

PythonLoopsFor LoopRange

Python Problem Overview


What is the pythonic way of looping through a range of numbers and skipping over one value? For example, the range is from 0 to 100 and I would like to skip 50.

Edit: Here's the code that I'm using

for i in range(0, len(list)):
    x= listRow(list, i)
    for j in range (#0 to len(list) not including x#)
        ...

Python Solutions


Solution 1 - Python

You can use any of these:

# Create a range that does not contain 50
for i in [x for x in xrange(100) if x != 50]:
    print i

# Create 2 ranges [0,49] and [51, 100] (Python 2)
for i in range(50) + range(51, 100):
    print i

# Create a iterator and skip 50
xr = iter(xrange(100))
for i in xr:
    print i
    if i == 49:
        next(xr)

# Simply continue in the loop if the number is 50
for i in range(100):
    if i == 50:
        continue
    print i

Solution 2 - Python

In addition to the Python 2 approach here are the equivalents for Python 3:

# Create a range that does not contain 50
for i in [x for x in range(100) if x != 50]:
    print(i)

# Create 2 ranges [0,49] and [51, 100]
from itertools import chain
concatenated = chain(range(50), range(51, 100))
for i in concatenated:
    print(i)

# Create a iterator and skip 50
xr = iter(range(100))
for i in xr:
    print(i)
    if i == 49:
        next(xr)

# Simply continue in the loop if the number is 50
for i in range(100):
    if i == 50:
        continue
    print(i)

Ranges are lists in Python 2 and iterators in Python 3.

Solution 3 - Python

It is time inefficient to compare each number, needlessly leading to a linear complexity. Having said that, this approach avoids any inequality checks:

import itertools

m, n = 5, 10
for i in itertools.chain(range(m), range(m + 1, n)):
    print(i)  # skips m = 5

As an aside, you woudn't want to use (*range(m), *range(m + 1, n)) even though it works because it will expand the iterables into a tuple and this is memory inefficient.


Credit: comment by njzk2, answer by Locke

Solution 4 - Python

for i in range(0, 101):
if i != 50:
    do sth
else:
    pass

Solution 5 - Python

for i in range(100):
    if i == 50:
        continue
    dosomething

Solution 6 - Python

It depends on what you want to do. For example you could stick in some conditionals like this in your comprehensions:

# get the squares of each number from 1 to 9, excluding 2
myList = [i**2 for i in range(10) if i != 2]
print(myList)

# --> [0, 1, 9, 16, 25, 36, 49, 64, 81]

Solution 7 - Python

This works for me;

example:

x = ['apple', 'orange', 'grape', 'lion', 'banana', 'watermelon', 'onion', 'cat',]

for xr in x:
    if xr in 'onion':
        print('onion is a vegetable')
        continue
    if (xr not in 'lion' and xr not in 'cat'):
        print(xr, 'is a fruit')

Output -->

apple is a fruit
orange is a fruit
grape is a fruit
banana is a fruit
watermelon is a fruit
onion is a vegetable

Solution 8 - Python

what you could do, is put an if statement around everything inside the loop that you want kept away from the 50. e.g.

for i in range(0, len(list)):
    if i != 50:
        x= listRow(list, i)
        for j in range (#0 to len(list) not including x#)

Attributions

All content for this solution is sourced from the original question on Stackoverflow.

The content on this page is licensed under the Attribution-ShareAlike 4.0 International (CC BY-SA 4.0) license.

Content TypeOriginal AuthorOriginal Content on Stackoverflow
QuestionDavidView Question on Stackoverflow
Solution 1 - Pythonnjzk2View Answer on Stackoverflow
Solution 2 - PythonSmittieView Answer on Stackoverflow
Solution 3 - PythonAsclepiusView Answer on Stackoverflow
Solution 4 - PythonMariaView Answer on Stackoverflow
Solution 5 - PythonDanielView Answer on Stackoverflow
Solution 6 - PythonMxLDevsView Answer on Stackoverflow
Solution 7 - PythonMohamed JawadView Answer on Stackoverflow
Solution 8 - PythonAnonemussView Answer on Stackoverflow