Python (Scripting) - if elif else statements
by
Jeremy Canfield |
Updated: October 21 2024
| Python (Scripting) articles
An if statement in Python has the following structure.
if <condition> :
<do something>
elif <condition>:
<do something>
else:
<do something>
For example.
if foo == "Hello":
print("foo equals Hello")
elif foo == "World":
print("foo equals World")
else:
print("foo does not equal Hello or World")
Following are command if statements.
| If variable or boolean is defined | see try except else NameError |
| If boolean is True or False | see Getting Started with Booleans |
| If the foo variable or list is empty | if foo == "": or if len(foo) == 0: |
| If the foo dict is empty | if bool(foo): or if len(foo) == 0: |
| If foo variable equals the bar variable | if foo == bar: |
| If foo variable does not equal the bar variable | if foo != bar: |
| Greater than | if foo > 12345: |
| Less than | if foo < 12345: |
| Greater than or equal to | if foo >= 12345: |
| Less than or equal to | if foo <= 12345: |
| If file or directory exists | import os.path if os.path.exists("/path/to/file.txt"): |
| If file or directory does not exist | import os.path if not os.path.exists("/path/to/file.txt"): |
| If file is empty | import os.path if os.path.getsize("/path/to/file.txt") == 0: |
| If a variable does or does not contain | see re.match |
| If list contains | see if string in list |
| if list does not contain | see if string in list |
| If the foo variable begins with Hello | see re.match if re.match('^Hello', foo): |
| match every other item (e.g. first item will be if, next item will be else - see this example) | if (item % 2): |
Multiple conditions
Multiple conditions can be evaluated by separating each condition with and or or.
if foo == "Hello" or foo == "World":
print("foo equals Hello or World")
else :
print("foo does not equal Hello or World")
Or like this, using and.
if foo == "Hello" and bar == "World":
print("foo equals Hello and bar equals World")
else :
print("foo does not equal Hello or bar does not equal World")
Here is another example.
if foo == "Hello" and (bar == "World" or bar == "Earth"):
print("foo equals Hello and bar equals World or Earth")
else :
print("foo does not equal Hello or bar does not equal World or Earth")
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