Basic types in python

Basic types in python#

Variables in python can hold different types of numbers and also other things such as text, images and more complex objects.

We can also print out the type of a variable.

Strings#

Variables can also hold text. We call them a “string” in this case, and define them by surrounding the value with either single quotes ' ' or double quotes " ":

workshop_name = "napari LatAm Workshop"
workshop_year = '2023'

Strings can be concatenated using the + operator:

workshop_name + workshop_year

'napari LatAm Workshop2023'

You can add a ‘space’ between strings like this:

workshop_name + " " + workshop_year

'napari LatAm Workshop 2023'

If we want to have single and double quotation marks within our text, we can put them in like this:

text = "He asked 'How can Voldemort be so good with computers?'."
print(text)

He asked 'How can Voldemort be so good with computers?'.

text = 'She answered "Because he is fluent in Python".'
print(text)

She answered "Because he is fluent in Python".

Combining strings and numbers#

When combining variables of numeric types and string types, errors may appear:

workshop_name + a

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
Cell In[12], line 1
----> 1 workshop_name + a

TypeError: can only concatenate str (not "int") to str

Those can be prevented by converting the numeric variable to a string type using the str() function:

workshop_name + str(a)

'napari LatAm Workshop2023'

You can also convert strings to numbers in case they contain numbers:

d = "5"

int(d)

a + int(d)

int("5")

f-strings#

Instead of having to manually convert numbers to strings in order to assemble them with other strings, we can resort to f-strings which are defined by simply adding an f before the opening quote of a regular string:

f"This is an f-string"

'This is an f-string'

We can now add variables directly in this text by surrounding them with curly brackets:

f"This is an f-string. a's value is {a}. Doubling the value of a gives {2*a}."

"This is an f-string. a's value is 2023. Doubling the value of a gives 4046."

As you can see above, f-strings can contain as many variables as needed and curly brackets can contain more than just a variable. We can even execute functions inside them:

f"The workshop_name variable contains {workshop_name.lower().count('r')} r letters."

'The workshop_name variable contains 2 r letters.'

Exercise#

Marie Curie’s name and birthdate are stored in variables. Concatenate them in one string variable and print it out. The output should be “Marie Curie, * 7 November 1867”

first_name = "Marie"
last_name = "Curie"

birthday_day = 7
birthday_month = "November"
birthday_year = 1867