python - Create and set an element of a Pandas DataFrame to a list -


i have pandas dataframe i'm creating row-by-row (i know, know, it's not pandorable/pythonic..). i'm creating elements using .loc so

output.loc[row_id, col_id]

and i'd set value empty list, []. 

output.loc[row_id, col_id] = []

unfortunately, error saying size of keys , values not match (pandas thinks i'm trying set values with not to iterable).

is there way this?

thanks!

you need make sure 2 things:

  1. there precisely 1 entry loc,
  2. the column has dtype object (actually, on testing seems not issue).

a hacky way use series []:

in [11]: df = pd.dataframe([[1, 2], [3, 4]], columns=['a', 'b'])  in [12]: df.loc[[0], 'a'] = pd.series([[]])  in [13]: df out[13]:      b 0  []  2 1   3  4

pandas doesn't want use [] elements because it's not efficient , makes aggregations more complicated (and un-cythonisable).

in general don't want build dataframes cell-by-cell, there (almost?) better way.


Comments

Post a Comment

Popular posts from this blog

javascript - RequestAnimationFrame not working when exiting fullscreen switching space on Safari -

request animation frame stops working when exiting fullscreen clicking on original space's safari window. fine if fullscreen mode canceled escape key or calling cancelfullscreen(). steps reproduce: open https://dl.dropboxusercontent.com/u/769042/prezi/safari-fullscreen.html click "draw raf", kittie appears click "fullscreen", go fullscreen click "draw raf", kittie appears go space original safari was, showing "click exit fullscreen mode", click anywhere, out fullscreen click "draw raf", nothing happens what handling click calling: window.requestanimationframe(draw); which draws on canvas context: function draw() { ctx.drawimage(img, math.random()*500|0, math.random()*400|0, 100, 100); } i checked .hidden , .visibilitystate, updated correctly. tested on osx 10.9.3, safari 7.0.4 (9537.76.4). has workaround/solution other switching old settimeout? this sounds webkit bug 88940 : using reque...
Read more

jsf - How to ajax update an item in the footer of a PrimeFaces dataTable? -

this visual of table have: +---------+------------+-------------------+ | header1 | header2 | header3 | +---------+------------+-------------------+ | row | input | calc'ed output | | row b | input b | calc'ed output b | | etc.. | etc.. | etc.. | +---------+------------+-------------------+ | total: total calc'ed output | +------------------------------------------+ and stripped-down code: <p:datatable id="mytable" value="#{mybean.somelist}" var="currentitem"> <p:column headertext="header1"> <h:outputtext value="#{currentitem.name}" /> </p:column> <p:column headertext="header2"> <pe:inputnumber value="#{currentitem.inputval}"> <p:ajax event="change" listener="#{mybean.changelistener}" update="outputval outputtotal...
Read more

jquery - Keeping Kendo Datepicker in min/max range -

when user types type in date outside of range, we're trying ensure date gets changed closest min/max. text displayed in date picker not change though thought script changing value() @(html.kendo() .datepickerfor(x => x.dob) .max(new datetime(datetime.now.addyears(-18).year, datetime.now.addyears(-18).month, datetime.now.addyears(-18).day)) .min(new datetime(datetime.now.addyears(-70).year, datetime.now.addyears(-70).month, datetime.now.addyears(-70).day)) .events(e=>e.change("ondobchange")) .htmlattributes(new { required = "required", ng_model = "model.dob" })) <p ng-show="validatestate.submitted && frmmain.dob.$invalid" class="help-block">please select</p> <script> function ondobchange(e) { var d...
Read more