Chapter 9
If Statements
Assume you need to know
whether the string allocated to the variable species is "cat."
This is the code.
1 if species == "cat":
2 print ("Yep, it's a cat.")
If the
string "feline" has been allocated to the variable species, Python
shows the message Yep, it's feline. On the off chance that the string
"feline" hasn't been appointed to the variable species, nothing
occurs.
We should figure out
down the code.
It starts with the
catchphrase if. Note that it is all lowercase. If you compose
If rather than if, it will not work. You'll
get a blunder message.
Note that it's two
equivalent signs, ==, not one. One
equivalent sign, =, must be utilized to
allocate an incentive to a variable, as in…
species = " cat "
At whatever point
you're trying whether one thing is equivalent to another, the administrator
must be ==. Else, you'll get a blunder
message.
The mainline closes
with a colon.
1 if species == " cat ":
If the
test passes—if the string "feline" has been allocated to the variable
species—you instruct Python. You place this
on its own line, and you indentation the line one tab.
1 if species == "cat":
2 print ("Yep, it's cat.")
You can make quite a
few things happen when the response to the if the question is "yes." Each
thing that happens gets its own line. What's more, each line is indented.
1 if species == "cat":
2 status = "Alright"
3 kingdoms = "animal"
4 print ("Yep, it's cat.")
There are different
things you can test, including numbers. It works the equivalent way…
1 if 2 + 2 == 4:
2 print ("Everything bodes
well.")
That test, obviously,
will consistently come out evident, and the message will be shown.
Here's another, that may not generally come out
obvious.
1 if some husbands == 1:
2 print ("So far so
great.")
In Python, indents
aren't only for a pretty design. They have significance for Python. They
aren't discretionary. All in all, any lines of code that take their orders from
a line that closes in a colon is indented. Examples:
1 if a number of husbands == 1:
2 print ("So far so
great.")
3 print("Congratulations.")
4 print ("All done")
In the code above,
lines 2 and 3 execute just if the if test in
line 1 passes.
Their execution is subject to what occurs in
line 1, so they're indented. Line 4 executes regardless. It runs freely of line
1, so it isn't indented.
What I'm saying here
isn't carefully precise. Later on, you'll see some code that doesn't exactly
fit what I'm saying. However, it's a helpful method to consider indents in
Python. As a dependable guideline.
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