# Loops

> Source: https://learn-python.com/loops/
> Part of Learn Python, free to read.

There are two types of loops in Python, for and while.

### The “for” loop

For loops iterate over a given sequence. Here is an example:

```python
primes = [2, 3, 5, 7]
for prime in primes:
    print(prime)
```

For loops can iterate over a sequence of numbers using the “range” and “xrange” functions. The difference between range and xrange is that the range function returns a new list with numbers of that specified range, whereas xrange returns an iterator, which is more efficient. (Python 3 uses the range function, which acts like xrange). Note that the range function is zero based.

```python
# Prints out the numbers 0,1,2,3,4
for x in range(5):
    print(x)

# Prints out 3,4,5
for x in range(3, 6):
    print(x)

# Prints out 3,5,7
for x in range(3, 8, 2):
    print(x)
```

### “while” loops

While loops repeat as long as a certain boolean condition is met. For example:

```python
# Prints out 0,1,2,3,4

count = 0
while count < 5:
    print(count)
    count += 1  # This is the same as count = count + 1
```

### “break” and “continue” statements

**break** is used to exit a for loop or a while loop, whereas **continue** is used to skip the current block, and return to the “for” or “while” statement. A few examples:

```python
# Prints out 0,1,2,3,4

count = 0
while True:
    print(count)
    count += 1
    if count >= 5:
        break

# Prints out only odd numbers - 1,3,5,7,9
for x in range(10):
    # Check if x is even
    if x % 2 == 0:
        continue
    print(x)
```

### Can we use “else” clause for loops?

Unlike languages like C,CPP.. we can use **else** for loops. When the loop condition of “for” or “while” statement fails then code part in “else” is executed. If a **break** statement is executed inside the for loop then the “else” part is skipped.
Note that the “else” part is executed even if there is a **continue** statement.

Here are a few examples:

```python
# Prints out 0,1,2,3,4 and then it prints "count value reached 5"

count=0
while(count<5):
    print(count)
    count +=1
else:
    print("count value reached %d" %(count))

# Prints out 1,2,3,4
for i in range(1, 10):
    if(i%5==0):
        break
    print(i)
else:
    print("this is not printed because for loop is terminated because of break but not due to fail in condition")
```