# 3.8 `for` Statement¶

- Repeat an action or several actions for each item in a sequence of items.
- A string is a sequence of individual characters.

In [1]:

    for character in 'Programming':
        print(character, end='  ')

    P  r  o  g  r  a  m  m  i  n  g

- Upon entering the `for` loop, Python assigns the 'P' in 'Programming' to the target variable between keywords `for` and `in`.
- After executing the suite, Python assigns to character the next item in the sequence (that is, the '`r`' in '`Programming`'), then executes the suite again.
- Continues while there are more items in the sequence.
- Using the target variable in the suite is common but not required.

### `for` Statement Flowchart¶

### Function `print`’s `end` Keyword Argument¶

- `print` displays its argument(s), then moves the cursor to the next line.
- Can change this behavior with the argument `end`:

  >     print(character, end='  ')

- `end` is a keyword argument, but it's not a Python keyword.
- The Style Guide for Python Code recommends placing no spaces around a keyword argument’s =.
- Keyword arguments are sometimes called named arguments.

### Function `print`’s `sep` Keyword Argument¶

- Keyword argument `sep` (short for separator) specifies the string that appears between the items that print displays.
- A space character by default.
- To remove the spaces, use an empty string with no characters between its quotes.

In [2]:

    print(10, 20, 30, sep=', ')

    10, 20, 30

## 3.8.1 Iterables, Lists and Iterators¶

- The sequence to the right of the `for` statement’s in keyword must be an iterable.
  - An object from which the `for` statement can take one item at a time.
- One of the most common iterables is a list, which is a comma-separated collection of items enclosed in square brackets (`[` and `]`).

In [3]:

    total = 0

In [4]:

    for number in [2, -3, 0, 17, 9]:
        total = total + number

In [5]:

    total

Out[5]:

    25

- Each sequence has an iterator.
- The for statement uses the iterator “behind the scenes” to get each consecutive item until there are no more to process.

## 3.8.2 Built-In `range` Function and Generators¶

- Creates an iterable object that represents a sequence of consecutive integer values starting from 0 and continuing up to, but not including, the argument value.

In [6]:

    for counter in range(10):
        print(counter, end=' ')

    0 1 2 3 4 5 6 7 8 9

### Off-By-One Errors¶

A logic error known as an off-by-one error occurs when you assume that `range`’s argument value is included in the generated sequence.

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