1.8 conditional statements

Important

This lesson is still under development.

The basic syntax of if statement in python is:

if (condition):
    do something

name = "zardari"

if name == 'zardari':
    print('chor')

chor

name = 'Zardari'
if name == 'zardari' or name == 'Zardari':
    print('chor')

chor

name = 'nawaz'
if name == 'zardari' or name == 'Zardari':
    print('chor')
if name == 'nawaz' or name == 'Nawaz':
    print('chor')

chor

Similarly the syntax for if and elif statement is

if (condition):
  do something
elif (condition):
  do something
else:
  do something

name = 'edhi'
if name == 'zardari' or name == 'Zardari':
    print(name, ' is chor')
elif name == 'nawaz' or name == 'Nawaz':
    print(name, ' is chor')
else:
    print(name, ' is not chor')

edhi  is not chor

elif vs multiple if

Multiple ifs means, the all the ifs will be checked, while with elif, the code will stop if one of the if is True.

age = 14

if age < 16:
    print("You are a child")
if age >= 16: #Greater than or equal to
    print("You are an adult")
else:   #Handle all cases where 'age' is negative
    print("The age must be a positive integer!")

You are a child
The age must be a positive integer!

age = 14

if age < 16:
       print("You are a child")
elif age > 16:
       print("You are an adult")
else:   #Handle all cases where 'age' is negative
       print("The age must be a positive integer!")

You are a child

in

We can use in statement to compare a variable against multiple variables.

name = 'zardari'
if name in ['zardari', 'nawaz', 'chaudhrys', 'mqm']:
    print(name, ' was democratic thug')
elif name in ['zia', 'yahya', 'musharaf', 'ayub']:
    print(name, ' was non-democratic thug')
else:
    print(name, ' is not chor')

zardari  was democratic thug

name = 'Zia'
if name.upper() in ['ZARDARI', 'NAWAZ', 'CHAUDHRYS', 'MQM']:
    print(name, ' was a democratic chor')
elif name.upper() in ['ZIA', 'YAHYA', 'MUSHARAF', 'AYUB']:
    print(name, ' was a non-democratic is chor')
else:
    print(name, ' is not chor')

Zia  was a non-democratic is chor

comparing numbers

year = 2009

if 2007>year>2000:
    print('Non-democratic thug ruled Pakistan')
elif 2020>year>=2007:
    print('democratic thug ruled Pakistan')
else:
    print('not considering')

democratic thug ruled Pakistan

year = 2012

if 2007>year>2000:
    print('Non-democratic thug ruled Pakistan')
elif 2020>year>=2007:

    if 2013>year>=2007:
        print('democratic thug zardari ruled Pakistan')
    elif 2018>year>=2013:
        print('democratic thug Nawaz ruled Pakistan')
    else:
        print('It seems the ruler is incapable')
else:
    print('not considering')

democratic thug zardari ruled Pakistan

One liner

day = "14 aug"

if day == '14 aug':  print('This is independence day not partition day.')

This is independence day not partition day.

oil = True
us_presence = 1 if oil else 0

print(us_presence)

1

We can use such one liners to set default values to a variable.

human = {"arms": 2,
         "legs": 2,
         "head": 1}

default_age = 14

age = human["age"] if "age" in human else default_age
print(age)

14

provinces = 4
capital = "Kathmandu"
pm = "unknown"

if provinces == 4 and capital == "Islamabad" or pm == "Imran Khan":
    print("This is Pakistan")

provinces = 4
capital = "unknown"
pm = "Imran Khan"

if provinces == 4 and capital == "Islamabad" or pm == "Imran Khan":
    print("This is Pakistan")

This is Pakistan

if not vs !=

Inner working is different but the output is same however not is preferred.

day = "Thursday"
if day != 'Friday':
    print('no jumma prayer')

no jumma prayer

day = "Thursday"
if not day == 'Friday':
    print('no jumma prayer')

no jumma prayer

if day == 'Friday':
    pass
else:
    print("no jumma prayer")

no jumma prayer

any vs all

a = [False, 2>4, 2!=1]
if any(a):
    print('go ahead')

go ahead

a = [False, 2>4, 2!=1]
if all(a):
    print('go ahead')