100 lines
2 KiB
Markdown
100 lines
2 KiB
Markdown
# Flow Control while, pass, break, continue
|
||
{:.no_toc}
|
||
|
||
<nav markdown="1" class="toc-class">
|
||
* TOC
|
||
{:toc}
|
||
</nav>
|
||
|
||
## The goal
|
||
|
||
While we wait...
|
||
|
||
Questions to [David Rotermund](mailto:davrot@uni-bremen.de)
|
||
|
||
**Logic blocks need to be indented. Preferable with 4 spaces!**
|
||
|
||
## [The while statement](https://docs.python.org/3/reference/compound_stmts.html#the-while-statement)
|
||
|
||
```python
|
||
i = 0
|
||
while i < 3:
|
||
print(i)
|
||
i += 1
|
||
```
|
||
|
||
Output
|
||
|
||
```python
|
||
0
|
||
1
|
||
2
|
||
```
|
||
|
||
## The full statement
|
||
|
||
```python
|
||
while_stmt ::= "while" assignment_expression ":" suite
|
||
["else" ":" suite]
|
||
```
|
||
|
||
## [pass](https://docs.python.org/3/reference/simple_stmts.html#the-pass-statement)
|
||
|
||
Since Python uses indents as definition for a functional block it needs pass for signaling an empty functional block.
|
||
|
||
> pass is a null operation — when it is executed, nothing happens. It is useful as a placeholder when a statement is required syntactically, but no code needs to be executed
|
||
|
||
```python
|
||
pass_stmt ::= "pass"
|
||
```
|
||
|
||
## [break](https://docs.python.org/3/reference/simple_stmts.html#the-break-statement)
|
||
|
||
> break may only occur syntactically nested in a for or while loop, but not nested in a function or class definition within that loop.
|
||
|
||
> It terminates the nearest enclosing loop, skipping the optional else clause if the loop has one.
|
||
|
||
> If a for loop is terminated by break, the loop control target keeps its current value.
|
||
|
||
```python
|
||
break_stmt ::= "break"
|
||
```
|
||
|
||
```python
|
||
for i in range(0, 5):
|
||
if i == 2:
|
||
break
|
||
print(i)
|
||
```
|
||
|
||
Output:
|
||
|
||
```python
|
||
0
|
||
1
|
||
```
|
||
|
||
|
||
## [continue](https://docs.python.org/3/reference/simple_stmts.html#the-continue-statement)
|
||
|
||
> continue may only occur syntactically nested in a for or while loop, but not nested in a function or class definition within that loop. It continues with the next cycle of the nearest enclosing loop.
|
||
|
||
```python
|
||
continue_stmt ::= "continue"
|
||
```
|
||
|
||
```python
|
||
for i in range(0, 5):
|
||
if i == 2:
|
||
continue
|
||
print(i)
|
||
```
|
||
|
||
Output:
|
||
|
||
```python
|
||
0
|
||
1
|
||
3
|
||
4
|
||
```
|