Python 3.8.12 | packaged by conda-forge | (default, Oct 12 2021, 21:50:38)

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IPython 7.29.0 -- An enhanced Interactive Python.

In [1]: 3*5

Out[1]: 15

In [2]: 3^5

Out[2]: 6

In [3]: 3**5

Out[3]: 243

In [4]: 51%5

Out[4]: 1

In [5]: 3

Out[5]: 3

In [6]: 51%3

Out[6]: 0

In [7]: aa=[[8,2],[42,42]] #list of lists - like a matrix

In [8]: aa+[4] # concatenates the two arrays

Out[8]: [[8, 2], [42, 42], 4]

In [9]: aa + 4

Traceback (most recent call last):

File "/var/folders/nj/tkk5x_7s3yn33fpszmyt7_d0p7__8q/T/ipykernel_12585/3168112346.py", line 1, in <module>

aa + 4

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

In [10]: cc = [j**2 for j in range(100)] # range(100) means 0 thru 99; list comprehension

In [11]: cc

Out[11]:

[0,

1,

4,

9,

16,

25,

36,

49,

64,

81,

100,

121,

144,

169,

196,

225,

256,

289,

324,

361,

400,

441,

484,

529,

576,

625,

676,

729,

784,

841,

900,

961,

1024,

1089,

1156,

1225,

1296,

1369,

1444,

1521,

1600,

1681,

1764,

1849,

1936,

2025,

2116,

2209,

2304,

2401,

2500,

2601,

2704,

2809,

2916,

3025,

3136,

3249,

3364,

3481,

3600,

3721,

3844,

3969,

4096,

4225,

4356,

4489,

4624,

4761,

4900,

5041,

5184,

5329,

5476,

5625,

5776,

5929,

6084,

6241,

6400,

6561,

6724,

6889,

7056,

7225,

7396,

7569,

7744,

7921,

8100,

8281,

8464,

8649,

8836,

9025,

9216,

9409,

9604,

9801]

In [12]: cc[0] # first element

Out[12]: 0

In [13]: aa[1] #second element (I mean row)

Out[13]: [42, 42]

In [14]: cc[-5:]

Out[14]: [9025, 9216, 9409, 9604, 9801]

In [15]: # last 5 elements of the list

In [16]: cc[90:]

Out[16]: [8100, 8281, 8464, 8649, 8836, 9025, 9216, 9409, 9604, 9801]

In [17]: cc[1:3]

Out[17]: [1, 4]

In [18]: cc[0:5]

Out[18]: [0, 1, 4, 9, 16]

In [19]: sum(cc)

Out[19]: 328350

In [20]: len(cc)

Out[20]: 100

In [21]: len(cc+cc+cc)

Out[21]: 300

In [22]: aa[1][0] means 2nd row, 1st column of our list of lists

File "/var/folders/nj/tkk5x_7s3yn33fpszmyt7_d0p7__8q/T/ipykernel_12585/401568039.py", line 1

aa[1][0] means 2nd row, 1st column of our list of lists

^

SyntaxError: invalid syntax

In [23]: aa[1][0] #means 2nd row, 1st column of our list of lists

Out[23]: 42

In [24]: def funTr(X):

    ...: if len(X)!=len(X[0]):

    ...: return "not a square matrix, dude"

    ...: else:

    ...: return sum([X[j][j] for j in range(len(X))])

    ...:

In [25]: # the if checks to make sure the #rows = #columns

In [26]: funTr(aa)

Out[26]: 50

In [27]: funTr(cc)

Traceback (most recent call last):

File "/var/folders/nj/tkk5x_7s3yn33fpszmyt7_d0p7__8q/T/ipykernel_12585/2722038734.py", line 1, in <module>

funTr(cc)

File "/var/folders/nj/tkk5x_7s3yn33fpszmyt7_d0p7__8q/T/ipykernel_12585/1446683790.py", line 2, in funTr

if len(X)!=len(X[0]):

TypeError: object of type 'int' has no len()

In [28]: bb=[[4,3,2,2],[3,2,2,1]]

In [29]: funTr(bb)

Out[29]: 'not a square matrix, dude'

In [30]: funTr(bb+bb)

Out[30]: 9

In [31]: runfile('/Users/richardson/Documents/2022S_na/python/classPy2022_01_20.py', wdir='/Users/richardson/Documents/2022S_na/python')

27

In [32]: runfile('/Users/richardson/Documents/2022S_na/python/classPy2022_01_20.py', wdir='/Users/richardson/Documents/2022S_na/python')

27

825

In [33]: