if statement python
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In Python you can define conditional statements, known as if-statements.
A block of code is executed if certain conditions are met.
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Consider this application, it executes either the first or second code depending on the value of x.
If you set x to be larger than 10, it will execute the second code block. We use indentation (4 spaces) to define the blocks.
A little game:
A variable may not always be defined by the user, consider this little game:
age = 24
A word on conditional operators
a = 12
This can quickly become difficult to read, consider combining 4 or 6 conditions. Luckily Python has a solution for this, we can combine conditions using the and keyword.
guess = 24
Sometimes you may want to use the or operator.
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In the first example the second print statement should, surely, read ;x is 10 or bigger' because the inequality test is for less than 10 not less than 11
Hi Ned, sorry my native language is not English. I updated it, thanks for the heads up!
Continually having problems with else, invalid syntax. (using 2.7.3)
Hi, syntax errors are usually related to spaces or typos. Could you post your code?
Under the "Conditional operators" section, for the sake of readability, aren't "lt;" and "less than" supposed to be on a line by themselves?
Right now, you've got "lt;" stuck to the end of "greater than", with "smaller than" in a column all to itself, and I'm pretty sure that that wasn't your intention.
Thanks Fred! It's been fixed
please can you help me, im doing interactive fiction in class on python and its very confusing please can you tell me how to make and correctly use a rucksack/ backpack, and why the sleep function isn't working
Hi, I think rucksack/backpack is something specific to your class. This is how to use the sleep function:
>>> if guess>10 and guess<20:
print "In range"
else:print "out of range"
after pressing the enter after writing the if block a error showing before entering the else block"IndentationError: expected an indented block". i am using python in OS X yosemite in terminal.
Hi Neil! Python uses indention very strictly, make sure every indent (block) is 4 spaces. Tabs or another amount of spaces than 4 will raise an error. Let me know how it works out.
as soon as i type in else: and press enter, it comes up SyntaxError : invalid syntax?
You are in the python interpreter directly. Use a text editor and save the text file as program.py then run it: python program.py
Alternatively use an IDE such as pycharm, komodo ide, atom + plugin.
How can you repeat this little game?
Do i need a while statement?Iam totaly new to this..
It depends on how many repetition you want. For an if-statement, the code will be executed onlyonce. If you don't know in advanced how many times the code will be executed, use a while loop.
for the IDE such as pycharm, komodo ide, atom + plugin, which one is best and which one is free? Could you suggest one?
It is a matter of preference, all of them use the same Python interpreter underneath.
Pycharm community edition is free. Atom + plugin is free. Komodo IDE is not free.
If you like a programming environment with many windows on the screen, go with PyCharm. For a minimalist appearance, use atom + script plugin. All of the IDEs use the same python programming language underneath.
Lately I like atom + script plugin a lot because of the minimalist appearance, it helps me to focus on the code and has a good UI. The script plugin can be installed from inside the atom IDE and programs run using the ctrl+shift+b shortcut. The PyCharm community edition runs out of the box and doesn't need additional plugins.
If you come from a .NET or Java background, there are Python plugins for Visual Studio, Netbeans and Eclipse.
A full list of programming environments can be found here
hello, I'm using a version 3.5 of Python which may be a little different from the tutorial. when I type "else" after "if", it always says invalid syntax. I'm totally confused of that.
Could you post the code you use? Make sure your indention is right. Python expects four spaces for every code block.
I am new to python and just learning the syntax. (I am experienced in other languages).
What is the syntax if I want more than one line of code between if: and else:, and more than one line after else: ?
Hi Erica, simply add the lines between if and lines. Python uses indention to define the code blocks. All lines should have the same indention. By default Python imposes four spaces.