I'm new to Python. Actually I implemented something using Java as shown below.
for(;;){
switch(expression){
case c1: statements
case c2: statements
default: statement
}
}
How do I implement this in Python?
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5 Answers
Use while loop:
while True:
if condition1:
statements
elif condition2:
statements
...
else:
statements
Comments
while True:
# do stuff forever
Comments
Formally, there's no switch statement in Python; it's a series of nested if-elif-else statements.
Infinite loops are accomplished by the while True statement.
All together:
while True:
if condition_1:
condition_1_function
elif condition_2:
condition_2_function
elif condition_3:
condition_3_function
else: # Always executes like "default"
condition_default_function
1 Comment
dcrosta
Beware that there is no fall-through in
if/elif/else like there would be in switchIf you are looking for a way to iterate infinitely in python you can use the itertools.count() function like a for loop. http://docs.python.org/py3k/library/itertools.html#itertools.count
2 Comments
hobs
This looks useful for infinite generator expressions like
('CONSTANT' for i in itertools.count(0, 0)) as an argument to functions expecting a generator. You don't have to define a separate function that has the while True loop.
flornquake
@hobs To achieve that, you would use
itertools.repeat('CONSTANT').You can use
while True:
if c1:
statements
elif c2:
statements
else:
statements
or
var = 1
while var == 1:
# do stuff
4 Comments
Makoto
Normally it's more implicit to use the boolean
True instead of an integer if we're talking infinite loops. This way, the intent is clearer and easier to debug (who's to say that the value of var may not change over time?).
Milo Casagrande
It is true, and using the boolean is (probably) the blessed way. That is just another example of achieving the same thing.
var can change, but that is also up to the developer to not change it if she chooses to go that way. ;-)
Ben
But why have
var at all? If the point is to have a value that is always equal to 1 to create an infinite loop, why not just say while 1 == 1? And having done that, it's absurd not to just write while True.Makoto
@Ben: We could go even further, and say
while 1, which is tantamount to while True. But that's quite besides the point! :)