# 4.3. Built-ins¶

## 4.3.1. Pi number¶

import numpy as np

np.pi
# 3.1415926535897931


## 4.3.2. Euler number¶

import numpy as np

np.e
# 2.7182818284590451


## 4.3.3. Infinite¶

import numpy as np

np.inf
# inf

np.Infinity
# inf

np.Inf
# inf

np.PINF
# inf

np.NINF
# -inf

-np.inf
# -inf

-np.Inf
# -inf

-np.Infinity
# -inf

import numpy as np

float('Inf')
# inf

float('Infinity')
# inf

float('inf')
# inf

np.inf == float('inf')
# True

np.inf is float('inf')
# False

import numpy as np

np.inf + 1          # inf
np.inf + np.inf     # inf
np.inf - np.inf     # nan
np.inf - np.nan     # nan

np.inf * np.inf     # inf
np.inf / np.inf     # nan

0 / np.inf          # 0.0
np.inf / 0          # ZeroDivisionError: float division by zero

import numpy as np

a = np.array([1, 2, np.inf])
# array([ 1.,  2., inf])

np.isfinite(a)
# array([ True,  True, False])

np.isinf(a)
# array([False, False,  True])

import numpy as np

a = np.array([1, 2, np.inf])
# array([ 1.,  2., inf])

np.isnan(a)
# array([False, False, False])


## 4.3.4. Not-a-Number¶

• Special float value

• Propagates in calculations

import numpy as np

np.NaN
# nan

np.NAN
# nan

np.nan
# nan

import numpy as np

float('nan')
# nan

np.nan is float('nan')
# False

np.nan == float('nan')
# False

np.nan is None
# False

np.nan == None
# False

import numpy as np

bool(None)
# False

bool(np.nan)
# True

import numpy as np

np.nan + 1          # nan
np.nan + np.nan     # nan
np.nan - np.nan     # nan
np.nan - np.inf     # nan

np.nan / np.nan     # nan
0 / np.nan          # nan
np.nan / 0          # ZeroDivisionError: float division by zero

import numpy as np

a = np.array([1, 2, np.nan])
# array([ 1.,  2., nan])

np.isnan(a)
# array([False, False,  True])

import numpy as np

a = np.array([1, 2, np.nan])
# array([ 1.,  2., nan])

np.isfinite(a)
# array([ True,  True, False])

np.isinf(a)
# array([False, False, False])


## 4.3.5. Assignments¶

Todo

Create assignments