Modify tick label text

Question

I want to make some modifications to a few selected tick labels in a plot   For example  if I do    label   axes yaxis get major ticks   2  label label set fontsize size  label set rotation  vertical     the font size and the orientation of the tick label is changed    However  if try   label set text  Foo     the tick label is not modified  Also if I do   print label get text     nothing is printed   Here s some more strangeness  When I tried this    from pylab import    axes   figure   add subplot 111   t   arange 0 0  2 0  0 01   s   sin 2 pi t   axes plot t  s   for ticklabel in axes get xticklabels         print ticklabel get text     Only empty strings are printed  but the plot contains ticks labeled as  0 0    0 5    1 0    1 5   and  2 0

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If you do not work with fig and ax and you want to modify all labels  e g  for normalization  you can do this   labels  locations   plt yticks   plt yticks labels  labels max labels

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I noticed that all the solutions posted here that use set xticklabels   are not preserving the offset  which is a scaling factor applied to the ticks values to create better-looking tick labels  For instance  if the ticks are on the order of 0 00001  1e-5   matplotlib will automatically add a scaling factor  or offset  of 1e-5  so the resultant tick labels may end up as 1 2 3 4  rather than 1e-5 2e-5 3e-5 4e-5  Below gives an example  The x array is np array  1  2  3  4   1e6  and y is y x  2  So both are very small values  Left column  manually change the 1st and 3rd labels  as suggested by  Joe Kington  Note that the offset is lost  Mid column  similar as  iipr suggested  using a FuncFormatter  Right column  My suggested offset-preserving solution  Figure here   Complete code here  import matplotlib pyplot as plt import numpy as np    create some  small  data to plot x   np arange 5  1e6 y   x  2  fig  axes   plt subplots 1  3  figsize  10 6     ------------------The set xticklabels   solution------------------ ax1   axes 0  ax1 plot x  y  fig canvas draw   labels    item get text   for item in ax1 get xticklabels       Modify specific labels labels 1     Testing  labels 3     Testing2  ax1 set xticklabels labels  ax1 set title  set xticklabels       --------------FuncFormatter solution-------------- import matplotlib ticker as mticker  def update ticks x  pos       if pos  1          return  testing      elif pos  3          return  testing2      else          return x  ax2 axes 1  ax2 plot x y  ax2 xaxis set major formatter mticker FuncFormatter update ticks   ax2 set title  Func Formatter     -------------------My solution------------------- def changeLabels axis  pos  newlabels          Change specific x y tick labels      Args          axis  Axis    xaxis or  yaxis obj          pos  list   indices for labels to change          newlabels  list   new labels corresponding to indices in  lt pos gt                if len pos     len newlabels           raise Exception  quot Length of  lt pos gt  doesn t equal that of  lt newlabels gt   quot        ticks   axis get majorticklocs         get the default tick formatter     formatter   axis get major formatter         format the ticks into strings     labels   formatter format ticks ticks         Modify specific labels     for pii  lii in zip pos  newlabels           labels pii    lii        Update the ticks and ticklabels  Order is important here        Need to first get the offset  1e-6 in this case       offset   formatter get offset         Then set the modified labels      axis set ticklabels labels        In doing so  matplotlib creates a new FixedFormatter and sets it to the xaxis       and the new FixedFormatter has no offset  So we need to query the       formatter again and re-assign the offset      axis get major formatter   set offset string offset       return  ax3   axes 2  ax3 plot x  y   changeLabels ax3 xaxis   1  3     Testing    Testing2    ax3 set title  With offset    fig show   plt savefig  tick labels png     Caveat  it appears that solutions that use set xticklabels    including my own  relies on FixedFormatter  which is static and doesn t respond to figure resizing  To observe the effect  change the figure to a smaller size  e g  fig  axes   plt subplots 1  3  figsize  6 6   and enlarge the figure window  You will notice that that only the mid column responds to resizing and adds more ticks as the figure gets larger  The left and right column will have empty tick labels  see figure below   Caveat 2  I also noticed that if your tick values are floats  calling set xticklabels ticks  directly might give you ugly-looking strings  like 1 499999999998 instead of 1 5

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Caveat  Unless the ticklabels are already set to a string  as is usually the case in e g  a boxplot   this will not work with any version of matplotlib newer than 1 1 0   If you re working from the current github master  this won t work   I m not sure what the problem is yet     It may be an unintended change  or it may not be     Normally  you d do something along these lines   import matplotlib pyplot as plt  fig  ax   plt subplots      We need to draw the canvas  otherwise the labels won t be positioned and    won t have values yet  fig canvas draw    labels    item get text   for item in ax get xticklabels    labels 1     Testing   ax set xticklabels labels   plt show       To understand the reason why you need to jump through so many hoops  you need to understand a bit more about how matplotlib is structured   Matplotlib deliberately avoids doing  static  positioning of ticks  etc  unless it s explicitly told to   The assumption is that you ll want to interact with the plot  and so the bounds of the plot  ticks  ticklabels  etc will be dynamically changing   Therefore  you can t just set the text of a given tick label   By default  it s re-set by the axis s Locator and Formatter every time the plot is drawn   However  if the Locators and Formatters are set to be static  FixedLocator and FixedFormatter  respectively   then the tick labels stay the same   This is what set  ticklabels or ax  axis set ticklabels does    Hopefully that makes it slighly more clear as to why changing an individual tick label is a bit convoluted   Often  what you actually want to do is just annotate a certain position   In that case  look into annotate  instead

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It s been a while since this question was asked  As of today  matplotlib 2 2 2  and after some reading and trials  I think the best proper way is the following   Matplotlib has a module named ticker that  contains classes to support completely configurable tick locating and formatting   To modify a specific tick from the plot  the following works for me   import matplotlib pyplot as plt import matplotlib ticker as mticker import numpy as np   def update ticks x  pos       if x    0          return  Mean      elif pos    6          return  pos is 6      else          return x  data   np random normal 0  1  1000  fig  ax   plt subplots   ax hist data  bins 25  edgecolor  black   ax xaxis set major formatter mticker FuncFormatter update ticks   plt show       Caveat  x is the value of the tick and pos is its relative position in order in the axis  Notice that pos takes values starting in 1  not in 0 as usual when indexing     In my case  I was trying to format the y-axis of a histogram with percentage values  mticker has another class named PercentFormatter that can do this easily without the need to define a separate function as before   import matplotlib pyplot as plt import matplotlib ticker as mticker import numpy as np   data   np random normal 0  1  1000  fig  ax   plt subplots   weights   np ones like data    len data  ax hist data  bins 25  weights weights  edgecolor  black   ax yaxis set major formatter mticker PercentFormatter xmax 1 0  decimals 1   plt show       In this case xmax is the data value that corresponds to 100   Percentages are computed as x   xmax   100  that s why we fix xmax 1 0  Also  decimals is the number of decimal places to place after the point

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Try this      fig axis   plt subplots nrows 1 ncols 1 figsize  13 6  sharex True    axis set xticklabels   0    testing    10000    20000    30000   fontsize 22

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In newer versions of matplotlib  if you do not set the tick labels with a bunch of str values  they are    by default  and when the plot is draw the labels are simply the ticks values   Knowing that  to get your desired output would require something like this    gt  gt  gt  from pylab import    gt  gt  gt  axes   figure   add subplot 111   gt  gt  gt  a axes get xticks   tolist    gt  gt  gt  a 1   change   gt  gt  gt  axes set xticklabels a    lt matplotlib text Text object at 0x539aa50 gt    lt matplotlib text Text object at 0x53a0c90 gt     lt matplotlib text Text object at 0x53a73d0 gt    lt matplotlib text Text object at 0x53a7a50 gt     lt matplotlib text Text object at 0x53aa110 gt    lt matplotlib text Text object at 0x53aa790 gt    gt  gt  gt  plt show     and the result    and now if you check the  xticklabels  they are no longer a bunch of       gt  gt  gt   item get text   for item in axes get xticklabels      0 0    change    1 0    1 5    2 0     It works in the versions from 1 1 1rc1 to the current version 2 0

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One can also do this with pylab and xticks  import matplotlib import matplotlib pyplot as plt x    0 1 2  y    90 40 65  labels     high    low   37337  plt plot x y   r   plt xticks x  labels  rotation  vertical   plt show     http   matplotlib org examples ticks and spines ticklabels demo rotation html

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you can do   for k in ax get xmajorticklabels        if some-condition          k set color any colour you like   draw

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The axes class has a set yticklabels function which allows you to set the tick labels  like so    ax is the axes instance group labels     control    cold treatment                 hot treatment    another treatment                 the last one    ax set xticklabels group labels    I m still working on why your example above didn t work

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This works   import matplotlib pyplot as plt  fig  ax1   plt subplots 1 1   x1    0 1 2 3  squad     Fultz   Embiid   Dario   Simmons    ax1 set xticks x1  ax1 set xticklabels squad  minor False  rotation 45

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This also works in matplotlib 3   x1    0 1 2 3  squad     Fultz   Embiid   Dario   Simmons    plt xticks x1  squad  rotation 45

[python] Modify tick label text

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