1 Basic data types

1.1 Integer

# python
a = 2
print(type(a))

## <class 'int'>

# R
a <- 2L # without the L, R makes this a numeric
str(a)

##  int 2

# python
b = 2.
print(type(b))

## <class 'float'>

# R
b <- 2
str(b)

##  num 2

# python
c = "2"
print(type(c))

## <class 'str'>

d = "two"
print(type(d))

## <class 'str'>

print(c + d) # python allows + to concatenate strings

## 2two

# R
c <- "2"
str(c)

##  chr "2"

d <- "two"
str(d)

##  chr "two"

tryCatch(c + d, error = function(e) warning(e)) # R does not allow + for strings
paste0(c, d) # use paste or paste0 functions instead

## [1] "2two"

# python
e = 2 + 2j
print(type(e))

## <class 'complex'>

# R
e <- 2+2i
str(e)

##  cplx 2+2i

# python
f = a == 2
print(type(f))

## <class 'bool'>

f = False # or True
print(type(f))

## <class 'bool'>

# R
f <- a == 2
str(f)

##  logi TRUE

f <- FALSE # or TRUE
str(f)

##  logi FALSE

# python
g = None
print(type(g))

## <class 'NoneType'>

# R
g <- NULL
str(g)

##  NULL

# python - ?
None

# R - NA constant defined for each basic data type
str(NA_integer_)

##  int NA

str(NA_real_)

##  num NA

str(NA_character_)

##  chr NA

str(NA_complex_)

##  cplx NA

str(NA)

##  logi NA

# python
shopping = ["pear", 2, 3.1459]
print(shopping)
# indices select list element and start with 0

## ['pear', 2, 3.1459]

print(shopping[1])

## 2

# R
shopping <- list("pear", 2, 3.1459)
str(shopping)

## List of 3
##  $ : chr "pear"
##  $ : num 2
##  $ : num 3.15

# indices select sub list and start with 1
str(shopping[1])

## List of 1
##  $ : chr "pear"

str(shopping[[1]]) # use [[]] to select list element

##  chr "pear"

# python
shopping.append("honey") 
shopping += ["sour cream"] # quick syntax for append
shopping[1] = [1, 2, 3] 
print(shopping)

## ['pear', [1, 2, 3], 3.1459, 'honey', 'sour cream']

# R
shopping <- c(shopping, list("honey", "sour cream")) 
shopping[2] <- list(1:3) 
shopping[[2]] <- 1:3 # same as above
str(shopping)

## List of 5
##  $ : chr "pear"
##  $ : int [1:3] 1 2 3
##  $ : num 3.15
##  $ : chr "honey"
##  $ : chr "sour cream"

# tuple
mytup = (1, 2., "3")
print(mytup)
# tuples cannot be changed

## (1, 2.0, '3')

try: 
  mytup[0] = 5
except:
  print("Unexpected error:", sys.exc_info()[1])

## Unexpected error: 'tuple' object does not support item assignment

# R - tuples do not exist, the one created in python is simply a regular list
str(py$mytup)

## List of 3
##  $ : int 1
##  $ : num 2
##  $ : chr "3"

# python
dict = {"spoons" : 5, "frog" : "green"}
print(dict)

## {'spoons': 5, 'frog': 'green'}

print(type(dict))

## <class 'dict'>

print(dict["frog"]) # select list element by name

## green

dict["gravity"] = 9.81 # re-assign list element by name
print(dict.keys()) # print all keys

## dict_keys(['spoons', 'frog', 'gravity'])

print(dict.values()) # print all values

## dict_values([5, 'green', 9.81])

# R - dictionaries don't exist separately, the one created in pythin is simply a named list
str(py$dict)

## List of 3
##  $ spoons : int 5
##  $ frog   : chr "green"
##  $ gravity: num 9.81

dict <- list("spoons" = 5, "frog" = "green", "no name") # mixed named and unnamed lists supported
str(dict)

## List of 3
##  $ spoons: num 5
##  $ frog  : chr "green"
##  $       : chr "no name"

dict$gravity <- 9.81 # modify by name
str(dict[[1]]) # select by index

##  num 5

str(dict$spoons) # or by name

##  num 5

str(names(dict)) # print all keys (names)

##  chr [1:4] "spoons" "frog" "" "gravity"

str(unname(dict)) # remove names to get values only

## List of 4
##  $ : num 5
##  $ : chr "green"
##  $ : chr "no name"
##  $ : num 9.81