Week 2: Functions#
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Exercise 2.1: Full name#
Complete the function full_name in file cp/ex02/full_name.py which takes as input two strings first_name and last_name. The function
should print a full name consisting of first_name and last_name with exactly one space character in between.
>>> full_name('Vedrana', 'Dahl')
Vedrana Dahl
>>> full_name('Morten', 'Hannemose')
Morten Hannemose
>>> full_name('Donald', 'Duck')
Donald Duck
- cp.ex02.full_name.full_name(first_name, last_name)#
Determine and print the full name given first name and last name.
- Parameters
first_name (
str) – your first name.last_name (
str) – your last name.
Exercise 2.2: Next thousand#
Complete the function next_thousand in file cp/ex02/next_thousand.next_thousand.py which takes as input a single number a. The function should print the value
of a rounded to the next thousand. For example:
>>> next_thousand(123998)
124000
>>> next_thousand(-123998)
-123000
- cp.ex02.next_thousand.next_thousand(a)#
Round a number to the next nearest thousand and print.
- Parameters
a (
int) – the number to be rounded.
Exercise 2.3: Name length#
Complete the function name_length in file cp/ex02/name_length.py which takes as input a string name. The function should print a message informing
about the length of name. For example, if name='Anika' the function should print "Your name consists of 5 characters."
>>> name_length('Anika')
Your name consists of 5 characters.
- cp.ex02.name_length.name_length(name)#
Calculate and print the number of characters in name.
- Parameters
name (
str) – your name.
Tip
To retrieve the length of the string, use build-in function len.
Exercise 2.4: Wind chill#
Complete the function wind_chill in file cp/ex02/wind_chill.py that takes as input the actual temperature temperature and the wind speed windspeed.
The function should print a message informing about the actual and the perceived temperature, with all numbers rounded to the nearest integer
(for example, 'Temperature: 17 degrees feels like 15 degrees.'). The perceived temperature is denoted by wind chill temperature \(T_{\mathrm{WC}}\).
The cooling effect depends on air temperature \(T\) and speed \(v\).
>>> wind_chill(8, 12.8)
Temperature: 8 degrees feels like 6 degrees.
>>> wind_chill(8, 25.8)
Temperature: 8 degrees feels like 4 degrees.
>>> wind_chill(-2, 12.8)
Temperature: -2 degrees feels like -6 degrees.
- cp.ex02.wind_chill.wind_chill(temperature, windspeed)#
Calculate and print the wind chill temperatures.
- Parameters
temperature (
int) – the actual temperature.windspeed (
float) – the wind speed.
Note
The following exercises are part of Project 1: Functions and printing. The link contains additional details, including how to hand in your results.
Exercise 2.5: Normal weight#
The body mass index (BMI) is defined as:
where \(w\) is body weight (mass) in kilograms, and \(h\) is the height in metres. A person is categorized as being of normal weight if the BMI falls in range from 18.5 to 25.
Implement the function normal_weight in file cp/ex02/normal_weight.py that takes height height in meters as input. The function should
print a message about normal weight range, given as the smallest and the largest weight in whole kilograms, which when converted to BMI fall into normal
range. The message should say, for example, 'Normal weight is between 56 and 74 kg.'
Example: for a given height h = 1.73, the limits of the normal weight range can be calculated as:
We need weight in whole kilograms and to ensure that weight falls into the normal range, the lower limit should be rounded up and the upper limit should be
rounded down. The function should print the message 'Normal weight is between 56 and 74 kg.'
>>> normal_weight(1.73)
Normal weight is between 56 and 74 kg.
- cp.ex02.normal_weight.normal_weight(height)#
Calculate and print the range of normal weights for a given height.
- Parameters
height (
float) – the height.
Exercise 2.6: Survival temperature#
To survive in cold temperatures, human must either maintain a sufficiently high metabolic rate, or regulate heat loss by covering their body with clothes made of insulating material. Given the metabolic heat production \(M\) and thermal conductance (for clothes and tissue) \(g\), the lowest temperature for survival \(T\) can be calculated by:
The reasonable range for metabolic heat production is from 50 for sleep to 500 for heavy activity, e.g. sports. The reasonable range for thermal conductance is from 0.04 for winter sleeping bag to 0.45 for no clothing.
Implement a function survival_temperature that takes the metabolic heat production \(M\) metabolic_heat and the thermal conductance \(g\)
thermal_conductance as input. The function should print a message about the survival temperature. For example, 'Survival temperature is -2.8 degrees.'. The
temperature should be rounded to the nearest 1 decimal place.
>>> survival_temperature(200, 0.1)
Survival temperature is -27.5 degrees.
- cp.ex02.survival_temperature.survival_temperature(metabolic_heat, thermal_conductance)#
Calculate and print the lowest survival temperature.
- Parameters
metabolic_heat (
int) – the metabolic heat production.thermal_conductance (
float) – the thermal conductance.
Exercise 2.7: Unit conversion#
Implement a function unit_conversion in file cp/ex02/unit_conversion.py that takes a length in foot and inch as input. The function should print a message about
the corresponding length in centimeter. For example, '7 ft 5 in is equal to 226 cm.'. The length should be rounded to the nearest integer.
Tip
1 foot = 12 inches
1 inch = 2.54 centimeters
>>> unit_conversion(7, 5)
7 ft 5 in is equal to 226 cm.
- cp.ex02.unit_conversion.unit_conversion(foot, inch)#
Convert length in foot and inch to centimeter.
- Parameters
foot (
int) – foot portion of the length in imperical unit.inch (
int) – inch portion of the length in imperical unit.
Exercise 2.8: Hadlock’s formula for fetal growth#
In obstetric ultrasound, fetal weight is widely used to monitor growth of the baby. This can be estimated from the ultrasound image by using the Hadlock’s formula:
where \(\mathrm{EFW}\) is the estimated fetal weight (g), \(\mathrm{HC}\) is the head circumference (cm), \(\mathrm{AC}\) is the abdominal circumference (cm), and \(\mathrm{FL}\) is the femur length (cm).
Implement a function hadlock in file cp/ex02/hadlock.py that takes the three measurements \(hc\) head_circ , \(ac\) abdomial_circ, and \(fl\) femur_length as input. The function
should print a message about the estimated fetal weight. For example, 'The estimated fetal weight is 2306.7 g.'. The estimated fetal weight
should be rounded to the nearest 1 decimal place.
>>> hadlock(31.1, 30.2, 8.3)
The estimated fetal weight is 2990.7 g.
- cp.ex02.hadlock.hadlock(head_circ, abdominal_circ, femur_length)#
Estimate fetal weight using Hadlock formula.
- Parameters
head_circ (
float) – head circumference in cm.abdominal_circ (
float) – abdominal circumference in cm.femur_length (
float) – femur length in cm.
Exercise 2.9 (optional): Keyword arguments and default values#
So far you’ve been writing Python functions that takes in one or more input arguments, perform a few computational steps, and print a message containing the results. In this exercise, we’ll explore how Python functions can be used in few other ways.
When multiple values are passed as input arguments to a function, it can be difficult to remember the order in which the arguments should be passed.
>>> def keyword_arguments_demo(arg1, arg2):
... print("arg1 is:", arg1, ", arg2 is: ", arg2)
...
>>> keyword_arguments_demo(7, 3)
arg1 is: 7 , arg2 is: 3
>>> keyword_arguments_demo(3, 7)
arg1 is: 3 , arg2 is: 7
However, we can specify the arguments by their names instead, which makes the code easier to read, especially when the variables have self explanatory names. We can give the arguments in an arbitrary order, as long as we specify the name of the argument.
>>> def keyword_arguments_demo(arg1, arg2):
... print("arg1 is:", arg1, ", arg2 is: ", arg2)
...
>>> keyword_arguments_demo(arg1=7, arg2=3)
arg1 is: 7 , arg2 is: 3
>>> keyword_arguments_demo(arg2=3, arg1=7)
arg1 is: 7 , arg2 is: 3
In many cases, it is useful to give default values to some of the inputs in the function definition. This allows us to call the function without specifying all the arguments:
>>> def keyword_arguments_demo(arg1=12, arg2=5):
... print("arg1 is:", arg1, ", arg2 is: ", arg2)
...
>>> keyword_arguments_demo(25, 7)
arg1 is: 25 , arg2 is: 7
>>> keyword_arguments_demo(25)
arg1 is: 25 , arg2 is: 5
>>> keyword_arguments_demo(arg2=7)
arg1 is: 12 , arg2 is: 7
Notice how the denominator has a default value of 3 when it’s not passed as input arguments to the function.
Your exercise is to try this out with your own functions!