Start a Loop from 1

Pythonic way to iterate through a range starting at 1

range(1, n+1) is not considered duplication, but I can see that this might become a hassle if you were going to change 1 to another number.

This removes the duplication using a generator:

for _ in (number+1 for number in range(5)):
    print(_)

Loop starting from 0 or 1? Which one and why?

1) No

2) Neither

3) Arrays in C and C++ are zero-based.

4) Yes.

Start a loop from 1

Ruby supports a number of ways of counting and looping:

1.upto(10) do |i|
  puts i
end

>> 1.upto(10) do |i|
 >     puts i
|    end #=> 1
1
2
3
4
5
6
7
8
9
10

There's also step instead of upto which allows you to increment by a step value:

>> 1.step(10,2) { |i| puts i } #=> 1
1
3
5
7
9

How to start from second index for for-loop

First thing is to remember that python uses zero indexing.

You can iterate throught the list except using the range function to get the indexes of the items you want or slices to get the elements.

What I think is becoming confusing here is that in your example, the values and the indexes are the same so to clarify I'll use this list as example:

I = ['a', 'b', 'c', 'd', 'e']
nI = len(I) # 5

The range function will allow you to iterate through the indexes:

for i in range(1, nI):
    print(i)
# Prints:
# 1
# 2
# 3
# 4

If you want to access the values using the range function you should do it like this:

for index in range(1, nI):
    i = I[index]
    print(i)
# Prints:
# b
# c
# d
# e

You can also use array slicing to do that and you don't even need nI. Array slicing returns a new array with your slice.

The slice is done with the_list_reference[start:end:steps] where all three parameters are optional and:

start is the index of the first to be included in the slice

end is the index of the first element to be excluded from the slice

steps is how many steps for each next index starting from (as expected) the start (if steps is 2 and start with 1 it gets every odd index).

Example:

for i in I[1:]:
    print(i)
# Prints:
# b
# c
# d
# e

Why is this for loop starting at index 1 instead of index 0?

When i=0, range(i) is empty, so it skips the inner loop:

>>> list(range(0))
[]

Skip first entry in for loop in python?

To skip the first element in Python you can simply write

for car in cars[1:]:
    # Do What Ever you want

or to skip the last elem

for car in cars[:-1]:
    # Do What Ever you want

You can use this concept for any sequence (not for any iterable though).

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