Python Package PrettyTable 终端表格工具
前言
在一次偶然的机会遇到了一个终端tool，里面的表格展示非常棒，翻看源码发现是一个名为PrettyTable的包，于是通过千难万阻后，终于找到了在维护开发的版本PTable
PrettyTable
原版已经在2013-04-07最后更新了
https://pypi.python.org/pypi/PrettyTable
PTable
其他开发者随后在
https://pypi.python.org/pypi/PTable
开始继续开发，并持续更新
Usage
import PrettyTable
1 | from prettytable import PrettyTable |
通过行创造，row by row
1 | x.field_names = ["City name", "Area", "Population", "Annual Rainfall"] |
逐列创建 Column by column
1 | x.add_column("City name", |
Mixing and matching
If you really want to, you can even mix and match add_row and add_column and build some of your table in one way and some of it in the other. There’s a unit test which makes sure that doing things this way will always work out nicely as if you’d done it using just one of the two approaches. Tables built this way are kind of confusing for other people to read, though, so don’t do this unless you have a good reason.
Importing data from a CSV file
If you have your table data in a comma separated values file (.csv), you can read this data into a PrettyTable like this:
1 | from prettytable import from_csv |
Importing data from a database cursor
If you have your table data in a database which you can access using a library which confirms to the Python DB-API (e.g. an SQLite database accessible using the sqlite module), then you can build a PrettyTable using a cursor object, like this:
1 | import sqlite3 |
Getting data out
There are three ways to get data out of a PrettyTable, in increasing order of completeness:
The del_row method takes an integer index of a single row to delete.
The clear_rows method takes no arguments and deletes all the rows in the table - but keeps the field names as they were so you that you can repopulate it with the same kind of data.
The clear method takes no arguments and deletes all rows and all field names. It’s not quite the same as creating a fresh table instance, though - style related settings, discussed later, are maintained.
Displaying your table in ASCII form
PrettyTable’s main goal is to let you print tables in an attractive ASCII form, like this:
1 | +-----------+------+------------+-----------------+ |
You can print tables like this to stdout or get string representations of them.
Printing
To print a table in ASCII form, you can just do this:
1 | print x |
in Python 2.x or:
1 | print(x) |
in Python 3.x.
The old x.printt() method from versions 0.5 and earlier has been removed.
To pass options changing the look of the table, use the get_string() method documented below:
1 | print x.get_string() |
Stringing
If you don’t want to actually print your table in ASCII form but just get a string containing what would be printed if you use “print x”, you can use the get_string method:
mystring = x.get_string()
This string is guaranteed to look exactly the same as what would be printed by doing “print x”. You can now do all the usual things you can do with a string, like write your table to a file or insert it into a GUI.
Controlling which data gets displayed
If you like, you can restrict the output of print x or x.get_string to only the fields or rows you like.
The fields argument to these methods takes a list of field names to be printed:
print x.get_string(fields=[“City name”, “Population”])
gives:
+———–+————+
| City name | Population |
+———–+————+
| Adelaide | 1158259 |
| Brisbane | 1857594 |
| Darwin | 120900 |
| Hobart | 205556 |
| Melbourne | 3806092 |
| Perth | 1554769 |
| Sydney | 4336374 |
+———–+————+
The start and end arguments take the index of the first and last row to print respectively. Note that the indexing works like Python list slicing - to print the 2nd, 3rd and 4th rows of the table, set start to 1 (the first row is row 0, so the second is row 1) and set end to 4 (the index of the 4th row, plus 1):
print x.get_string(start=1,end=4)
prints:
+———–+——+————+—————–+
| City name | Area | Population | Annual Rainfall |
+———–+——+————+—————–+
| Brisbane | 5905 | 1857594 | 1146.4 |
| Darwin | 112 | 120900 | 1714.7 |
| Hobart | 1357 | 205556 | 619.5 |
+———–+——+————+—————–+
Changing the alignment of columns
By default, all columns in a table are centre aligned.
All columns at once
You can change the alignment of all the columns in a table at once by assigning a one character string to the align attribute. The allowed strings are “l”, “r” and “c” for left, right and centre alignment, respectively:
x.align = “r”
print x
gives:
+———–+——+————+—————–+
| City name | Area | Population | Annual Rainfall |
+———–+——+————+—————–+
| Adelaide | 1295 | 1158259 | 600.5 |
| Brisbane | 5905 | 1857594 | 1146.4 |
| Darwin | 112 | 120900 | 1714.7 |
| Hobart | 1357 | 205556 | 619.5 |
| Melbourne | 1566 | 3806092 | 646.9 |
| Perth | 5386 | 1554769 | 869.4 |
| Sydney | 2058 | 4336374 | 1214.8 |
+———–+——+————+—————–+
One column at a time
You can also change the alignment of individual columns based on the corresponding field name by treating the align attribute as if it were a dictionary.
x.align[“City name”] = “l”
x.align[“Area”] = “c”
x.align[“Population”] = “r”
x.align[“Annual Rainfall”] = “c”
print x
gives:
+———–+——+————+—————–+
| City name | Area | Population | Annual Rainfall |
+———–+——+————+—————–+
| Adelaide | 1295 | 1158259 | 600.5 |
| Brisbane | 5905 | 1857594 | 1146.4 |
| Darwin | 112 | 120900 | 1714.7 |
| Hobart | 1357 | 205556 | 619.5 |
| Melbourne | 1566 | 3806092 | 646.9 |
| Perth | 5386 | 1554769 | 869.4 |
| Sydney | 2058 | 4336374 | 1214.8 |
+———–+——+————+—————–+
Sorting your table by a field
You can make sure that your ASCII tables are produced with the data sorted by one particular field by giving get_string a sortby keyword argument, which > must be a string containing the name of one field.
For example, to print the example table we built earlier of Australian capital city data, so that the most populated city comes last, we can do this:
print x.get_string(sortby=”Population”)
to get
+———–+——+————+—————–+
| City name | Area | Population | Annual Rainfall |
+———–+——+————+—————–+
| Darwin | 112 | 120900 | 1714.7 |
| Hobart | 1357 | 205556 | 619.5 |
| Adelaide | 1295 | 1158259 | 600.5 |
| Perth | 5386 | 1554769 | 869.4 |
| Brisbane | 5905 | 1857594 | 1146.4 |
| Melbourne | 1566 | 3806092 | 646.9 |
| Sydney | 2058 | 4336374 | 1214.8 |
+———–+——+————+—————–+
If we want the most populated city to come first, we can also give a reversesort=True argument.
If you always want your tables to be sorted in a certain way, you can make the setting long term like this:
x.sortby = “Population”
print x
print x
print x
All three tables printed by this code will be sorted by population (you could do x.reversesort = True as well, if you wanted). The behaviour will persist until you turn it off:
x.sortby = None
If you want to specify a custom sorting function, you can use the sort_key keyword argument. Pass this a function which accepts two lists of values and returns a negative or positive value depending on whether the first list should appeare before or after the second one. If your table has n columns, each list will have n+1 elements. Each list corresponds to one row of the table. The first element will be whatever data is in the relevant row, in the column specified by the sort_by argument. The remaining n elements are the data in each of the table’s columns, in order, including a repeated instance of the data in the sort_by column.
Changing the appearance of your table - the easy way
By default, PrettyTable produces ASCII tables that look like the ones used in SQL database shells. But if can print them in a variety of other formats as well. If the format you want to use is common, PrettyTable makes this very easy for you to do using the set_style method. If you want to produce an uncommon table, you’ll have to do things slightly harder (see later).
Setting a table style
You can set the style for your table using the set_style method before any calls to print or get_string. Here’s how to print a table in a format which works nicely with Microsoft Word’s “Convert to table” feature:
from prettytable import MSWORD_FRIENDLY
x.set_style(MSWORD_FRIENDLY)
print x
In addition to MSWORD_FRIENDLY there are currently two other in-built styles you can use for your tables:
DEFAULT - The default look, used to undo any style changes you may have made
PLAIN_COLUMN - A borderless style that works well with command line programs for columnar data
Other styles are likely to appear in future releases.
Changing the appearance of your table - the hard way
If you want to display your table in a style other than one of the in-built styles listed above, you’ll have to set things up the hard way.
Don’t worry, it’s not really that hard!
Style options
PrettyTable has a number of style options which control various aspects of how tables are displayed. You have the freedom to set each of these options individually to whatever you prefer. The set_style method just does this automatically for you.
The options are these:
border - A boolean option (must be True or False). Controls whether > > or not a border is drawn around the table.
header - A boolean option (must be True or False). Controls whether > > or not the first row of the table is a header showing the names of all the > > fields.
hrules - Controls printing of horizontal rules after rows. Allowed > > values: FRAME, HEADER, ALL, NONE - note that these are variables defined > > inside the prettytable module so make sure you import them or use > > prettytable.FRAME etc.
vrules - Controls printing of vertical rules between columns. Allowed > > values: FRAME, ALL, NONE.
int_format - A string which controls the way integer data is printed. > > This works like: print “%
float_format - A string which controls the way floating point data is > > printed. This works like: print “%
padding_width - Number of spaces on either side of column data (only used > > if left and right paddings are None).
left_padding_width - Number of spaces on left hand side of column data.
right_padding_width - Number of spaces on right hand side of column data.
vertical_char - Single character string used to draw vertical lines. > > Default is |.
horizontal_char - Single character string used to draw horizontal lines. > > Default is -.
junction_char - Single character string used to draw line junctions. > > Default is +.
You can set the style options to your own settings in two ways:
Setting style options for the long term
If you want to print your table with a different style several times, you can set your option for the “long term” just by changing the appropriate attributes. If you never want your tables to have borders you can do this:
x.border = False
print x
print x
print x
Neither of the 3 tables printed by this will have borders, even if you do things like add extra rows inbetween them. The lack of borders will last until you do:
x.border = True
to turn them on again. This sort of long term setting is exactly how set_style works. set_style just sets a bunch of attributes to pre-set values for you.
Note that if you know what style options you want at the moment you are creating your table, you can specify them using keyword arguments to the constructor. For example, the following two code blocks are equivalent:
x = PrettyTable()
x.border = False
x.header = False
x.padding_width = 5
x = PrettyTable(border=False, header=False, padding_width=5)
Changing style options just once
If you don’t want to make long term style changes by changing an attribute like in the previous section, you can make changes that last for just one get_string by giving those methods keyword arguments. To print two “normal” tables with one borderless table between them, you could do this:
print x
print x.get_string(border=False)
print x
Displaying your table in HTML form
PrettyTable will also print your tables in HTML form, as
| City name | Area | Population | Annual Rainfall |
|---|---|---|---|
| Adelaide | 1295 | 1158259 | 600.5 |
| Brisbane | 5905 | 1857594 | 1146.4 | ... ... ...
x.format = True
and the setting will persist until you turn it off.
Just like with ASCII tables, if you want to change the table’s style for just one print_html or one get_html_string you can pass those methods keyword arguments - exactly like print and get_string.
Setting HTML attributes
You can provide a dictionary of HTML attribute name/value pairs to the print_html and get_html_string methods using the attributes keyword argument. This lets you specify common HTML attributes like name, id and class that can be used for linking to your tables or customising their appearance using CSS. For example:
x.print_html(attributes={“name”:”my_table”, “class”:”red_table”})
will print:
| City name | Area | Population | Annual Rainfall |
|---|
Copying a table
You can call the copy method on a PrettyTable object without arguments to return an identical independent copy of the table.
If you want a copy of a PrettyTable object with just a subset of the rows, you can use list slicing notation:
new_table = old_table[0:5]
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