Python2.7 Self-paced note using Python as a calculator

1. Number

Numbers can be used directly in Python operations, using parentheses to group

In [1]: 2+2out[1]: 4In [2]: 50-5*6out[2]: 20In [3]: (50-5.0*6)/4out[3]: 5.0In [4]: 8/5.0out[4]: 1.6

In the case of division/, if the 2 divisor is of type int, the returned value is also integral int:

If there are 1 divisor of float float, then the result value is float type float;

With the operator//division, the returned value is the rounding

Use% to do division to take remainder;

In [5]: 17/3out[5]: 5In [6]: 17/3.0out[6]: 5.666666666666667In [7]: 17//3.0out[7]: 5.0In [8]: 17%3out[8]: 2

Use * * To calculate the exponentiation:

In [9]: 5**2out[9]: 25In [ten]: 2**7out[10]: 128

To assign a value using the = sign:

In [all]: width=20in []: height=5*9in []: Width * heightout[13]: 900

If a variable is not defined, then using it directly will make an error:

in [+]: N---------------------------------------------------------------------------nameerror  Traceback (most recent) <ipython-input-14-fe13119fb084> in <module> ()----> 1 nnameerror:name ' n ' is not defined

Conversion of integral and floating-point types:

In []: 3*3.75/1.5out[15]: 7.5In [+]: 7.0/2out[16]: 3.5

The result of the last printed calculation can be given directly to the "_" symbol

in [+]: tax=12.5/100in []: price=100.50in [+]: Tax * priceout[19]: 12.5625In []: price+_out[20]: 113.0625In [+]: RO und (_,2) out[21]: 113.06

2, String

You can use single quotation marks and double quotation marks to refer to a string directly, and a backslash to escape quotation marks:

in [+]: ' Spam eggs ' out[22]: ' Spam eggs ' in [all]: ' doesn\ ' t ' out[23]: ' doesn ' t ' in []: ' doesn ' t ' out[24]: ' doesn ' t ' in [25]: ' Yes, ' he said. ' OUT[25]: ' Yes, ' he said. ' in []: "\" yes,\ "he said." OUT[26]: ' Yes, ' he said. ' in [+]: ' "isn\ ' t," she said. OUT[27]: ' isn\ ' t, ' she said. '

Use the Print command to ignore character quotes and to print special meaning symbols:

in [+]: ' isn\ ' t, ' she said. ' OUT[28]: ' isn\ ' t, ' she said. ' In []: print ' "isn\ ' t," she said. " Isn ' t, "she said." in [+]: s = ' first line.\nsecond line. ' in [+]: sout[31]: ' First line.\nsecond line. ' in [+]: print Sfirst line. Second line.

If you don't want to print a special character, you can precede the first quotation mark with R:

in [+]: print ' C:\some\name ' C:\someameIn [+]: Print R ' C\some\name ' C\some\name

You can put more than one line in a row by using the quotation marks, but the plus \ symbol after the first quotation mark will still use multiline mode:

in [38]: print  "" "   ....: Usage: thingy [OPTIONS]    ....:      -h                         Display this  usage message   ....:      -h hostname                hostname to connect  to   ....:  "" "Usage: thingy [options]     -h                          display this usage message     -h  hostname                Hostname to connect to

String can use the + sign join or the * number operation

in [+]: 3 * ' un ' + ' ium ' out[40]: ' Unununium '

Connecting multiple strings can be used in the following ways:

in []: ' Py ' ' thon ' out[42]: ' Python '

Use the + symbol to concatenate a variable with a string:

In ["]: prefix = ' Py ' in []: prefix + ' thon ' out[44]: ' Python '

Using quotation marks is useful when you need to concatenate long strings together:

In []: Text = (' Put several strings within parentheses ' ....: ' To has them joined together. ') in [+]: textout[46]: ' Put several strings within parentheses to has them joined together. '

A string can have an index:

in [+]: Word = ' Python ' in [word[0]out[48]: ' P ' in [ps]: word[5]out[49]: ' n ' in [+]: word[-1]out[50]: ' n ' in [Wuyi]: Wor D[-2]OUT[51]: ' O ' in [Page]: word[-6]out[52]: ' P '

Slice of string:

in [+]: word[0:2]out[53]: ' Py ' in [si]: word[2:5]out[54]: ' tho ' in []: Word[:2] + word[2:]out[55]: ' Python ' in []: word[ : 4] + word[4:]out[56]: ' Python '

The string slice index shows:

+---+---+---+---+---+---+ | P | y | T | H | o | n | +---+---+---+---+---+---+ 0 1 2 3 4 5 6-6-5-4-3-2-1

Slices that exceed the index order can be handled more amicably:

In [the]: word[4:42]out[68]: ' On ' in []: word[42:]

String cannot be changed:

In []: word[0] = ' J '---------------------------------------------------------------------------TypeError Traceback (most recent) <ipython-input-69-197b67ffdd83> in <module> ()----> 1 word [0] = ' J ' TypeError: ' str ' object does not a support item assignment

If you need a different string, you can generate a new string:

In [all]: ' J ' + word[1:]out[70]: ' Jython ' in [[]: Word[:2] + ' py ' out[71]: ' PyPy '

Use the built-in Len function to calculate the length of a string:

In [out[72]: Len (word): 6

This article is from the "Ordinary Road" blog, please be sure to keep this source http://linjohn.blog.51cto.com/1026193/1608530

Python2.7 Self-paced note using Python as a calculator