if
elif
else
and, or, not
True
and False
Examples
x = 5.5
if x < 10: # note the ":"
print("x < 10")
x < 10
if x < 3 :
print("x < 3")
else : # note the "else"
print("x >= 3")
x >= 3
if x < 3 :
print("x < 3")
elif x < 4 : # note the "elif"
print("x < 4")
if x < 3 :
print("x < 3")
elif x < 4 :
print("x < 4")
else: # else to cap it off
print("x >= 4")
x >= 4
if x < 3 :
print("x<3")
elif x < 5 : # multiple elif
print("x<5")
elif x > 5 :
print("x>5")
else :
print("something else")
x>5
x = 5.5
if (x > 3 and x < 6) or x <= 1 :
print("made it")
print("Doing some more stuff in here")
print("Can have multiple lines. ")
print("Blank lines don't matter.") # note the use of the single and double quotes
print("Indent all lines inside the block at the same level")
made it Doing some more stuff in here Can have multiple lines. Blank lines don't matter. Indent all lines inside the block at the same level
Can use variables or expressions in if
statements
Tmin = 298.15
T = 500
if T < Tmin :
print("Warning, T<Tmin")
if T > Tmin*10 :
print("Warning, T>10*Tmin")
if Tmin <= T and T <= 10*Tmin:
print("All is well with T, nice work.")
All is well with T, nice work.
Scope: variables declared outside the if statement can be seen inside.
Tmin = 298.15
T = 500
if T> Tmin:
print("T =", T)
T = 500
Here is a condensed if
statement:
T = 298.15 if x<5.0 else 500.0 # single line if statement
print("x=", x, ", T=", T)# note: sep='' changes the separation character
x= 5.5 , T= 500.0
Example
Take the the square root, and make the argument positive if its negative:
x = -9
print(x**0.5)
y = (x if x>=0 else -x)**0.5
print("y = ", y)
(1.8369701987210297e-16+3j) y = 3.0